@article{
	11391_1420339,
	author = {Bistarelli, Stefano and Rossi, Fabio and Santini, Francesco},
	title = {A novel weighted defence and its relaxation in abstract argumentation},
	year = {2018},
	journal = {INTERNATIONAL JOURNAL OF APPROXIMATE REASONING},
	volume = {92},
	abstract = {When dealing with Weighted Abstract Argumentation, having weights on attacks clearly brings more information. The advantage, for instance, is the possibility to define a different notion of defence, checking also if the weight associated with it is stronger than the attack weight. In this work we study two different relaxations, one related to the new weighted defence we propose, by checking the difference between the composition of inward and outward attack-weights. The second one is related to how much inconsistency we are willing to tolerate inside an extension; such amount is computed by aggregating the costs of the attacks between any two arguments both inside an extension. These two relaxations are strictly linked: allowing a small conflict may lead to have more arguments into an extension, and consequently result in a stronger or weaker defence. Weights are represented by a semiring structure, which can be instantiated to different metrics used in the literature (e.g., costs, probabilities, fuzzy levels).},
	keywords = {Abstract Argumentation Frameworks; Inconsistency tolerance; Relaxation; Semirings; Weighted attacks; Software; Theoretical Computer Science; Artificial Intelligence; Applied Mathematics},
	doi = {10.1016/j.ijar.2017.10.006},	
	pages = {66--86}
}

When dealing with Weighted Abstract Argumentation, having weights on attacks clearly brings more information. The advantage, for instance, is the possibility to define a different notion of defence, checking also if the weight associated with it is stronger than the attack weight. In this work we study two different relaxations, one related to the new weighted defence we propose, by checking the difference between the composition of inward and outward attack-weights. The second one is related to how much inconsistency we are willing to tolerate inside an extension; such amount is computed by aggregating the costs of the attacks between any two arguments both inside an extension. These two relaxations are strictly linked: allowing a small conflict may lead to have more arguments into an extension, and consequently result in a stronger or weaker defence. Weights are represented by a semiring structure, which can be instantiated to different metrics used in the literature (e.g., costs, probabilities, fuzzy levels).

@inbook{
	11391_1417228,
	author = {Bistarelli, Stefano and Ceberio, Martine and Henderson, Joel A. and Santini, Francesco},
	title = {Abstract argumentation frameworks to promote fairness and rationality in multi-experts multi-criteria decision making},
	year = {2018},
	publisher = {Springer International Publishing},
	volume = {100},
	booktitle = {Studies in Systems, Decision and Control},
	abstract = {In this work, we propose to model Multi-Experts Multi-CriteriaDecision-Making (MEMCDM) problems using Abstract Argumentation Frameworks. We specifically design our model so as to ensure fairness and rationality in the decision-making process. For instance, when, of two expert’s decisions, one is unfair, we impose an attack between these two decisions, forcing one of the two decisions out of the argumentation network’s resulting extensions. Similarly, we specifically put irrational decisions in opposition to force one out. In doing so, we aim to enable the prediction of decisions that are themselves fair and rational. Our model is illustrated on a toy example.},
	keywords = {Computer Science (miscellaneous); Decision Sciences (miscellaneous); 2001; Automotive Engineering; Control and Systems Engineering; Control and Optimization; Social Sciences (miscellaneous)},
	url = {www.springer.com/series/13304},
	doi = {10.1007/978-3-319-61753-4_2},	
	pages = {7--19}
}

In this work, we propose to model Multi-Experts Multi-CriteriaDecision-Making (MEMCDM) problems using Abstract Argumentation Frameworks. We specifically design our model so as to ensure fairness and rationality in the decision-making process. For instance, when, of two expert’s decisions, one is unfair, we impose an attack between these two decisions, forcing one of the two decisions out of the argumentation network’s resulting extensions. Similarly, we specifically put irrational decisions in opposition to force one out. In doing so, we aim to enable the prediction of decisions that are themselves fair and rational. Our model is illustrated on a toy example.

@conference{
	11391_1427783,
	author = {Bistarelli, Stefano and Parroccini, Matteo and Santini, Francesco},
	title = {Visualising bitcoin flows of ransomware: WannaCry one week later},
	year = {2018},
	publisher = {CEUR-WS},
	volume = {2058},
	booktitle = {CEUR Workshop Proceedings},
	abstract = {Because of its pseudo-anonimity and decentralisation characteristics, bitcoin payments are often a tool utilised by ransomware: this kind of malware infects a victim computer by encrypting some/all its data and/or denying the access to it. Then, the victim has to pay a given amount of bitcoins to see all the blocked functionalities restored. The goal of this paper is to visualise these bitcoin transactions, and in particular we focus on the effects of one of such ransomware, i.e., WannaCry, one/two weeks after its diffusion. We exploit Block Chain Vis, a tool for visualising flows of bitcoins through the use of Visual Analytics.},
	keywords = {Computer Science (all)},
	url = {http://ceur-ws.org/Vol-2058/}
}

Because of its pseudo-anonimity and decentralisation characteristics, bitcoin payments are often a tool utilised by ransomware: this kind of malware infects a victim computer by encrypting some/all its data and/or denying the access to it. Then, the victim has to pay a given amount of bitcoins to see all the blocked functionalities restored. The goal of this paper is to visualise these bitcoin transactions, and in particular we focus on the effects of one of such ransomware, i.e., WannaCry, one/two weeks after its diffusion. We exploit Block Chain Vis, a tool for visualising flows of bitcoins through the use of Visual Analytics.

@inbook{
	11391_1420696,
	author = {Garbayo, Luciana and Ceberio, Martine and Bistarelli, Stefano and Henderson, Joel},
	title = {On modeling multi-experts multi-criteria decision-making argumentation and disagreement: Philosophical and computational approaches reconsidered},
	year = {2018},
	publisher = {Springer International Publishing},
	volume = {100},
	booktitle = {Studies in Systems, Decision and Control},
	abstract = {In this article we suggest that the research area of epistemology of disagreement should be critically applied to the problem of describing multi-experts multi-criteria decision-making (ME-MCDM), while providing an epistemic conceptualization of experts as epistemic peers. We explore some preliminary outcomes of using Dung’s computational framework for argumentation in ME-MCDM with conceptual considerations on the role of formal constraints and rationality approaches for epistemic peer disagreement, such as provided by David Christensen [2], inclusive of epistemic and pragmatic rationality, synchronic and diachronic rationality, and global and local aspects thereof},
	url = {www.springer.com/series/13304},
	doi = {10.1007/978-3-319-61753-4_10},	
	pages = {67--75}
}

In this article we suggest that the research area of epistemology of disagreement should be critically applied to the problem of describing multi-experts multi-criteria decision-making (ME-MCDM), while providing an epistemic conceptualization of experts as epistemic peers. We explore some preliminary outcomes of using Dung’s computational framework for argumentation in ME-MCDM with conceptual considerations on the role of formal constraints and rationality approaches for epistemic peer disagreement, such as provided by David Christensen [2], inclusive of epistemic and pragmatic rationality, synchronic and diachronic rationality, and global and local aspects thereof

@article{
	11391_1425840,
	author = {Bistarelli, Stefano and Rossi, Fabio and Santini, Francesco},
	title = {Not only size, but also shape counts: Argumentation solvers are benchmark-sensitive},
	year = {2018},
	journal = {JOURNAL OF LOGIC AND COMPUTATION},
	volume = {28},
	abstract = {We test different solvers dedicated to the solution of classical problems in Argumentation, as enumeration/existence of extensions, and sceptical/credulous acceptance of arguments. We handle a subset of the solvers tested in ICCMA15, and a superset of graphs used in the same competition. The goal is to provide considerations that can help future comparisons and competitions as ICCMA15. We offer a detailed report of this comparison from the point of view of different graphs, solvers, problems and timeouts. We show that the characteristics of graphs impact on the performance of solvers and on their final ranking. In addition, we extract other general considerations, e.g., reducing the computation timeout does not change the same ranking.},
	keywords = {argumentation; benchmark; graph models; reasoning tools; Theoretical Computer Science; Software; Arts and Humanities (miscellaneous); Hardware and Architecture; Logic},
	url = {http://logcom.oxfordjournals.org/},
	doi = {10.1093/logcom/exx031},	
	pages = {85--117}
}

We test different solvers dedicated to the solution of classical problems in Argumentation, as enumeration/existence of extensions, and sceptical/credulous acceptance of arguments. We handle a subset of the solvers tested in ICCMA15, and a superset of graphs used in the same competition. The goal is to provide considerations that can help future comparisons and competitions as ICCMA15. We offer a detailed report of this comparison from the point of view of different graphs, solvers, problems and timeouts. We show that the characteristics of graphs impact on the performance of solvers and on their final ranking. In addition, we extract other general considerations, e.g., reducing the computation timeout does not change the same ranking.

@article{
	11391_1357705,
	author = {Bistarelli, Stefano and Santini, Francesco},
	title = {On merging two trust-networks in one with bipolar preferences},
	year = {2017},
	journal = {MATHEMATICAL STRUCTURES IN COMPUTER SCIENCE},
	volume = {27},
	abstract = {In this paper, we study weighted trust-networks (but also unweighted), where each edge is associated with either a positive or a negative score. Hence, we consider a distrust relationship as well, allowing a user to rate poor experiences with other individuals in his web of acquaintances. We propose an algorithm to compose two of such networks in a single one, in order to merge the knowledge obtained in two different communities of individuals (possibly partially-overlapping), through two different trust management-systems. Our algorithm is based on semiring algebraic-structures, in order to have a parametric computational-framework. Such composition can be adopted whenever two trust-based communities (with the same scope) need to be amalgamated: for instance, two competitor-companies that need to unify the trust-based knowledge on their (sub-) suppliers.},
	doi = {10.1017/S0960129515000092},	
	pages = {215--233}
}

In this paper, we study weighted trust-networks (but also unweighted), where each edge is associated with either a positive or a negative score. Hence, we consider a distrust relationship as well, allowing a user to rate poor experiences with other individuals in his web of acquaintances. We propose an algorithm to compose two of such networks in a single one, in order to merge the knowledge obtained in two different communities of individuals (possibly partially-overlapping), through two different trust management-systems. Our algorithm is based on semiring algebraic-structures, in order to have a parametric computational-framework. Such composition can be adopted whenever two trust-based communities (with the same scope) need to be amalgamated: for instance, two competitor-companies that need to unify the trust-based knowledge on their (sub-) suppliers.

@article{
	11391_1398932,
	author = {Benedetti, Irene and Bistarelli, Stefano},
	title = {From Argumentation Frameworks to Voting Systems and Back},
	year = {2017},
	journal = {FUNDAMENTA INFORMATICAE},
	volume = {150},
	abstract = {Formal voting theories are established and can be used to determine if a voting system is fair or not in order to preserve democracy. There are a lot of voting systems described in the literature, with several properties, useful in many contexts. The Argumentation Framework is based on the exchange and the evaluation of interacting arguments which may represent information of various kinds. We show that Argumentation Frameworks can be interpreted within a voting theory and considered as voting methods. Using a mapping that associates an argument to a candidate and attacks to votes, we define a bidirectional mapping between the two theories and investigate how fairness criteria defined for voting systems can be re-interpreted within Argumentation Framework. We also show how voting ballots can be seen as suitable semantics for Argumentation Frameworks.},
	doi = {10.3233/FI-2017-1459},	
	pages = {25--48}
}

Formal voting theories are established and can be used to determine if a voting system is fair or not in order to preserve democracy. There are a lot of voting systems described in the literature, with several properties, useful in many contexts. The Argumentation Framework is based on the exchange and the evaluation of interacting arguments which may represent information of various kinds. We show that Argumentation Frameworks can be interpreted within a voting theory and considered as voting methods. Using a mapping that associates an argument to a candidate and attacks to votes, we define a bidirectional mapping between the two theories and investigate how fairness criteria defined for voting systems can be re-interpreted within Argumentation Framework. We also show how voting ballots can be seen as suitable semantics for Argumentation Frameworks.

@conference{
	11391_1417230,
	author = {Bistarelli, Stefano and Santini, Francesco},
	title = {A hasse diagram for weighted sceptical semantics with a unique-status grounded semantics},
	year = {2017},
	publisher = {Springer Verlag},
	volume = {10377},
	booktitle = {Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)},
	abstract = {We provide an initial study on the Hasse diagram that represents the partial order -w.r.t. set inclusion- among weighted sceptical semantics in Argumentation: grounded, ideal, and eager. Being our framework based on a parametric structure of weights, we can directly compare weighted and classical approaches. We define a unique-status weighted grounded semantics, and we prove that the lattice of stronglyadmissible extensions becomes a semi-lattice.},
	keywords = {Theoretical Computer Science; Computer Science (all)},
	url = {http://springerlink.com/content/0302-9743/copyright/2005/},
	doi = {10.1007/978-3-319-61660-5_6},	
	pages = {49--56}
}

We provide an initial study on the Hasse diagram that represents the partial order -w.r.t. set inclusion- among weighted sceptical semantics in Argumentation: grounded, ideal, and eager. Being our framework based on a parametric structure of weights, we can directly compare weighted and classical approaches. We define a unique-status weighted grounded semantics, and we prove that the lattice of stronglyadmissible extensions becomes a semi-lattice.

@conference{
	11391_1419867,
	author = {Bistarelli, Stefano and Di Noia, Tommaso and Mongiello, Marina and Nocera, Francesco},
	title = {PrOnto: An Ontology Driven Business Process Mining Tool},
	year = {2017},
	publisher = {Elsevier B.V.},
	journal = {PROCEDIA COMPUTER SCIENCE},
	volume = {112},
	booktitle = {Knowledge-Based and Intelligent Information & Engineering Systems: Proceedings of the 21st International Conference, KES-20176-8 September 2017, Marseille, France},
	keywords = {activity diagram; business process mining; ontology; Computer Science (all)},
	url = {http://www.sciencedirect.com/science/journal/18770509},
	doi = {10.1016/j.procs.2017.08.002},	
	pages = {306--315}
}

@conference{
	11391_1409310,
	author = {Bistarelli, Stefano and Martinelli, Fabio and Matteucci, Ilaria and Santini, Francesco},
	title = {A formal and run-time framework for the adaptation of local behaviours to match a global property},
	year = {2017},
	publisher = {Springer Verlag},
	volume = {10231},
	booktitle = {Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)},
	abstract = {We address the problem of automatically identifying what local properties the agents of a Cyber Physical System have to satisfy to guarantee a global required property φ. To enrich the picture, we consider properties where, besides qualitative requirements on the actions to be performed, we assume a weight associated with them: quantitative properties are specified through a weighted modal-logic. We propose both a formal machinery based on a Quantitative Partial Model Checking function on contexts, and a run-time machinery that algorithmically tries to check if the local behaviours proposed by the agents satisfy φ. The proposed approach can be seen as a run-time decomposition, privacysensitive in the sense agents do not have to disclose their full behaviour.},
	keywords = {Computer software; Embedded systems; Machinery; Model checking, Local property; Modal logic; Partial model checking; Runtimes},
	url = {http://springerlink.com/content/0302-9743/copyright/2005/},
	doi = {10.1007/978-3-319-57666-4_9},	
	pages = {134--152}
}

We address the problem of automatically identifying what local properties the agents of a Cyber Physical System have to satisfy to guarantee a global required property φ. To enrich the picture, we consider properties where, besides qualitative requirements on the actions to be performed, we assume a weight associated with them: quantitative properties are specified through a weighted modal-logic. We propose both a formal machinery based on a Quantitative Partial Model Checking function on contexts, and a run-time machinery that algorithmically tries to check if the local behaviours proposed by the agents satisfy φ. The proposed approach can be seen as a run-time decomposition, privacysensitive in the sense agents do not have to disclose their full behaviour.

@conference{
	11391_1417229,
	author = {Bistarelli, Stefano and Mantilacci, Marco and Santancini, Paolo and Santini, Francesco},
	title = {An end-to-end voting-system based on Bitcoin},
	year = {2017},
	publisher = {Association for Computing Machinery},
	volume = {128005},
	booktitle = {Proceedings of the ACM Symposium on Applied Computing},
	abstract = {In this work we re-adapt the Bitcoin e-payment system and propose it as a decentralised end-to-end voting platform (from voters to candidates). We describe the main architectural choices behind the implementation, which consists of the pre-voting, voting, and post-voting phases. The resulting implementation is completely decentralised: it is possible to directly cast a vote in the block-chain without any collecting intermediate-level. All the votes can be verified by anyone reading such a public ledger. We also exploit digital asset coins to directly keep track of votes (through the Open Asset Protocol), and we show the election cost for n voters.},
	keywords = {Bitcoin; Electronic voting; Verifiable voting-system; Software},
	doi = {10.1145/3019612.3019841},	
	pages = {1836--1841}
}

In this work we re-adapt the Bitcoin e-payment system and propose it as a decentralised end-to-end voting platform (from voters to candidates). We describe the main architectural choices behind the implementation, which consists of the pre-voting, voting, and post-voting phases. The resulting implementation is completely decentralised: it is possible to directly cast a vote in the block-chain without any collecting intermediate-level. All the votes can be verified by anyone reading such a public ledger. We also exploit digital asset coins to directly keep track of votes (through the Open Asset Protocol), and we show the election cost for n voters.

@conference{
	11391_1420338,
	author = {Bistarelli, Stefano and Santini, Francesco},
	title = {Go with the -bitcoin- flow, with visual analytics},
	year = {2017},
	publisher = {Association for Computing Machinery},
	volume = {130521},
	booktitle = {ACM International Conference Proceeding Series},
	abstract = {Bitcoin is a cryptocurrency and a peer-to-peer payment system, where transactions directly take place between pseudo-anonymous users, without any centralised authority. Bitcoin pseudo-anonymity can be -also- a cover for financing crime or for money laundering, as the existence of some illegal markets on the Dark Web proves. Since the block-chain (i.e., the public ledger where transactions are registered) is an example of Big Data, a straightforward visualisation is not much informative. For this reason, we employ techniques from Visual Analytics to filter out undesired information in order to obtain a tool to visually analyse the transactions and help its analysis.},
	keywords = {Analysis tool; Bitcoin; Visual analytics; Human-Computer Interaction; Computer Networks and Communications; 1707; Software},
	url = {http://portal.acm.org/},
	doi = {10.1145/3098954.3098972},	
	pages = {1--6}
}

Bitcoin is a cryptocurrency and a peer-to-peer payment system, where transactions directly take place between pseudo-anonymous users, without any centralised authority. Bitcoin pseudo-anonymity can be -also- a cover for financing crime or for money laundering, as the existence of some illegal markets on the Dark Web proves. Since the block-chain (i.e., the public ledger where transactions are registered) is an example of Big Data, a straightforward visualisation is not much informative. For this reason, we employ techniques from Visual Analytics to filter out undesired information in order to obtain a tool to visually analyse the transactions and help its analysis.

@inbook{
	11391_1423107,
	author = {Bistarelli, Stefano and Giacomin, Massimiliano and Pazienza, Andrea},
	title = {Preface of the 1st Workshop on Advances In Argumentation In Artificial Intelligence, AI^3 2017},
	year = {2017},
	publisher = {CEUR-WS},
	volume = {2012},
	booktitle = {CEUR Workshop Proceedings},
	keywords = {Argumentation, computer science},
	url = {http://ceur-ws.org/}
}

@conference{
	11391_1431560,
	author = {Bistarelli, Stefano and Giuliodori, Paolo and Mugnai, Dimitri},
	title = {A community payment scheme for consciousness energy usage},
	year = {2017},
	publisher = {Institute of Electrical and Electronics Engineers Inc.},
	volume = {2017-},
	booktitle = {2017 AEIT International Annual Conference: Infrastructures for Energy and ICT: Opportunities for Fostering Innovation, AEIT 2017},
	keywords = {energy behaviour change; fair cost division; payment scheme; Shapley value; Energy Engineering and Power Technology; Biomedical Engineering; Renewable Energy, Sustainability and the Environment},
	doi = {10.23919/AEIT.2017.8240545},	
	pages = {1--6}
}

@misc{
	11391_1391865,
	author = {Bistarelli, Stefano and Formisano, Andrea},
	title = {Theoretical Computer Science in Italy},
	year = {2016},
	publisher = {Elsevier},
	address = {Amsterdam, Netherlands},
	journal = {THEORETICAL COMPUTER SCIENCE},
	volume = {629},
	keywords = {Theoretical Computer Science; Computer Science (all)},
	url = {http://www.journals.elsevier.com/theoretical-computer-science/},
	doi = {10.1016/j.tcs.2016.04.010},	
	pages = {1--1}
}

@conference{
	11391_1398837,
	author = {Bistarelli, Stefano and Culmone, Rosario and Giuliodori, Paolo and Mugnoz, Stefano},
	title = {A mechanism design approach for allocation of commodities},
	year = {2016},
	publisher = {CEUR-WS},
	volume = {1720},
	booktitle = {CEUR Workshop Proceedings},
	abstract = {We deploy a mechanism design approach for allocating a divisible commodity (electricity in our example) among consumers. We
consider each consumer with an associated personal valuation function of the energy resource during a certain time interval. We aim to select the
optimal consumption profile for every user avoiding consumption peaks when the total required energy could exceed the energy production. The
mechanism will be able to drive users in shifting energy consumptions in different hours of the day. We start by presenting a very basic Vickrey-
Clarke-Groves mechanism, we discuss its weakness and propose several more complex variants. This is an extended abstract, for additional details we provide a technical report},
	url = {http://ceur-ws.org/Vol-1720/short10.pdf},
	pages = {275--279}
}

We deploy a mechanism design approach for allocating a divisible commodity (electricity in our example) among consumers. We consider each consumer with an associated personal valuation function of the energy resource during a certain time interval. We aim to select the optimal consumption profile for every user avoiding consumption peaks when the total required energy could exceed the energy production. The mechanism will be able to drive users in shifting energy consumptions in different hours of the day. We start by presenting a very basic Vickrey- Clarke-Groves mechanism, we discuss its weakness and propose several more complex variants. This is an extended abstract, for additional details we provide a technical report

@misc{
	11391_1395417,
	author = {Bistarelli, Stefano and Formisano, Andrea and Maratea, Marco},
	title = {RCRA 2016
International Workshop on Experimental Evaluation of Algorithms for Solving Problems with Combinatorial Explosion},
	year = {2016},
	publisher = {CEUR-WS.org},
	volume = {1745},
	abstract = {This volume contains the papers presented at RCRA 2016, the 23rd RCRA International Workshop on “Experimental Evaluation of Algorithms for Solving Problems with Combinatorial Explosion” held on November 28, 2016 in Genova.},
	url = {http://ceur-ws.org/Vol-1745/},
	pages = {1--104}
}

This volume contains the papers presented at RCRA 2016, the 23rd RCRA International Workshop on “Experimental Evaluation of Algorithms for Solving Problems with Combinatorial Explosion” held on November 28, 2016 in Genova.

@conference{
	11391_1398691,
	author = {Bistarelli, Stefano and Santini, Francesco and Martinelli, Fabio and Matteucci, Ilaria},
	title = {Automated adaptation via Quantitative Partial Model Checking},
	year = {2016},
	publisher = {Association for Computing Machinery},
	volume = {04-08-},
	booktitle = {Proceedings of the ACM Symposium on Applied Computing},
	abstract = {We propose a formal framework to model an automated adaptation protocol based on Quantitative Partial Model Checking (QPMC). An agent seeks the collaboration of a second agent to satisfy some (fixed) condition on the actions to be executed. The provided protocol allows the two agents to automatically agree by iteratively applying QPMC.},
	keywords = {Adaptation; Partial model checking, multi-agent systems; Software},
	doi = {10.1145/2851613.2851955},	
	pages = {1993--1996}
}

We propose a formal framework to model an automated adaptation protocol based on Quantitative Partial Model Checking (QPMC). An agent seeks the collaboration of a second agent to satisfy some (fixed) condition on the actions to be executed. The provided protocol allows the two agents to automatically agree by iteratively applying QPMC.

@conference{
	11391_1398697,
	author = {Bistarelli, Stefano and Rossi, Fabio and Santini, Francesco},
	title = {A relaxation of internal conflict and defence in weighted argumentation frameworks},
	year = {2016},
	publisher = {Springer Verlag},
	volume = {10021},
	booktitle = {Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)},
	abstract = {In Weighted Abstract Argumentation Frameworks (WAAFs), weights on attacks bring more information. An advantage is the possibility to define a different notion of defence, which also checks if the weight associated with defence is compared with the weight of attacks. We study and merge together two different relaxations of classically crisp-concepts in WAAFs: one is related to a new notion of weighted defence (defence can be stronger or weaker at will), while the second one is related to how much inconsistency one is willing to tolerate inside an extension (which can be not totally conflict-free now). These two relaxations are strictly related and influence each other: allowing a small conflict may lead to have more arguments in an extension, and consequently result in a stronger or weaker defence. We model weights with a semiring structure, which can be instantiated to different metrics used in the literature (e.g., fuzzy WAAFs).},
	keywords = {Theoretical Computer Science; Computer Science (all)},
	url = {http://springerlink.com/content/0302-9743/copyright/2005/},
	doi = {10.1007/978-3-319-48758-8_9},	
	pages = {127--143}
}

In Weighted Abstract Argumentation Frameworks (WAAFs), weights on attacks bring more information. An advantage is the possibility to define a different notion of defence, which also checks if the weight associated with defence is compared with the weight of attacks. We study and merge together two different relaxations of classically crisp-concepts in WAAFs: one is related to a new notion of weighted defence (defence can be stronger or weaker at will), while the second one is related to how much inconsistency one is willing to tolerate inside an extension (which can be not totally conflict-free now). These two relaxations are strictly related and influence each other: allowing a small conflict may lead to have more arguments in an extension, and consequently result in a stronger or weaker defence. We model weights with a semiring structure, which can be instantiated to different metrics used in the literature (e.g., fuzzy WAAFs).

@conference{
	11391_1398698,
	author = {Bistarelli, Stefano and Rossi, Fabio and Santini, Francesco},
	title = {A collective defence against grouped attacks for weighted abstract argumentation frameworks},
	year = {2016},
	publisher = {AAAI Press},
	booktitle = {Proceedings of the 29th International Florida Artificial Intelligence Research Society Conference, FLAIRS 2016},
	abstract = {Adding weights or preferences to Abstract Argumentation Frameworks can help disentangle semantics from otherwise all-equivalent attacks. Having such information makes possible to distil the set of found extensions by reducing their number. In this work we provide a new definition of weighted defence: according to it, all the attacks from an argument to a set of arguments are considered with a single global weight, i.e., attacks are grouped together. This provides a coherent view w.r.t. defence, which is usually “collective” in the literature. Moreover, we model weighted defences from related works in the same algebraic framework: this allows us to compare all the different proposals together.},
	keywords = {Software; Artificial Intelligence; Computer Networks and Communications},
	pages = {638--643}
}

Adding weights or preferences to Abstract Argumentation Frameworks can help disentangle semantics from otherwise all-equivalent attacks. Having such information makes possible to distil the set of found extensions by reducing their number. In this work we provide a new definition of weighted defence: according to it, all the attacks from an argument to a set of arguments are considered with a single global weight, i.e., attacks are grouped together. This provides a coherent view w.r.t. defence, which is usually “collective” in the literature. Moreover, we model weighted defences from related works in the same algebraic framework: this allows us to compare all the different proposals together.

@conference{
	11391_1398838,
	author = {Bistarelli, Stefano and Rossi, Fabio and Santini, Francesco},
	title = {ConArg: A Tool for Classical and Weighted Argumentation},
	year = {2016},
	publisher = {IOS Press},
	booktitle = {Frontiers in Artificial Intelligence and Applications},
	abstract = {ConArg is a tool for solving different problems related to extension-based semantics: e.g., enumeration of extensions, sceptical and credulous acceptance of arguments. We have extended it in order to deal with Weighted Abstract Argumentation Frameworks, where each attack is associated with a strength score. Classical notions of defence and conflict-freeness have been redefined with the purpose to have different (weighted) degrees of their relaxation. The ultimate aim is to let an agent choose between a higher internal consistency or a stronger defence.},
	doi = {10.3233/978-1-61499-686-6-463},	
	pages = {463--464}
}

ConArg is a tool for solving different problems related to extension-based semantics: e.g., enumeration of extensions, sceptical and credulous acceptance of arguments. We have extended it in order to deal with Weighted Abstract Argumentation Frameworks, where each attack is associated with a strength score. Classical notions of defence and conflict-freeness have been redefined with the purpose to have different (weighted) degrees of their relaxation. The ultimate aim is to let an agent choose between a higher internal consistency or a stronger defence.

@misc{
	11391_1399092,
	author = {Bistarelli, Stefano and Formisano, Andrea and Maratea, Marco and Torroni, Paolo},
	title = {Special issue of the 22nd RCRA international workshop on "Experimental Evaluation of Algorithms for Solving Problems with Combinatorial Explosion"},
	year = {2016},
	publisher = {IOS Press},
	address = {;Nieuwe Hemweg 6B},
	journal = {FUNDAMENTA INFORMATICAE},
	volume = {149},
	keywords = {Theoretical Computer Science; Algebra and Number Theory; Information Systems; Computational Theory and Mathematics},
	url = {http://www.iospress.nl/},
	doi = {10.3233/FI-2016-1440},	
	pages = {v--vii}
}

@inbook{
	11391_1431179,
	author = {Bistarelli, Stefano and Formisano, Andrea and Maratea, Marco},
	title = {Preface},
	year = {2016},
	publisher = {CEUR-WS},
	volume = {1745},
	booktitle = {CEUR Workshop Proceedings},
	keywords = {Computer Science (all)},
	url = {http://ceur-ws.org/}
}

@article{
	11391_1342078,
	author = {Bistarelli, Stefano and Gabbrielli, Maurizio and Meo, MARIA CHIARA and Santini, Francesco},
	title = {Timed soft concurrent constraint programs: An interleaved and a parallel approach},
	year = {2015},
	journal = {THEORY AND PRACTICE OF LOGIC PROGRAMMING},
	volume = {15},
	abstract = {We propose a timed and soft extension of Concurrent Constraint Programming. The time extension is based on the hypothesis of bounded asynchrony: The computation takes a bounded period of time and is measured by a discrete global clock. Action prefixing is then considered as the syntactic marker that distinguishes a time instant from the next one. Supported by soft constraints instead of crisp ones, tell and ask agents are now equipped with a preference (or consistency) threshold, which is used to determine their success or suspension. In this paper, we provide a language to describe the agents' behavior, together with its operational and denotational semantics, for which we also prove the compositionality and correctness properties. After presenting a semantics using maximal parallelism of actions, we also describe a version for their interleaving on a single processor (with maximal parallelism for time elapsing). Coordinating agents that need to take decisions on both preference values and time events may benefit from this language.},
	keywords = {interleaving, parallelism, Soft Concurrent Constraint Programming, Timed Concurrent Constraint Programming},
	doi = {10.1017/S1471068414000106},	
	pages = {1--743}
}

We propose a timed and soft extension of Concurrent Constraint Programming. The time extension is based on the hypothesis of bounded asynchrony: The computation takes a bounded period of time and is measured by a discrete global clock. Action prefixing is then considered as the syntactic marker that distinguishes a time instant from the next one. Supported by soft constraints instead of crisp ones, tell and ask agents are now equipped with a preference (or consistency) threshold, which is used to determine their success or suspension. In this paper, we provide a language to describe the agents' behavior, together with its operational and denotational semantics, for which we also prove the compositionality and correctness properties. After presenting a semantics using maximal parallelism of actions, we also describe a version for their interleaving on a single processor (with maximal parallelism for time elapsing). Coordinating agents that need to take decisions on both preference values and time events may benefit from this language.

@article{
	11391_1357699,
	author = {Bistarelli, Stefano and Rossi, Fabio and Santini, Francesco},
	title = {A Comparative Test on the Enumeration of Extensions in Abstract Argumentation},
	year = {2015},
	journal = {FUNDAMENTA INFORMATICAE},
	volume = {140},
	abstract = {We compare four different implementations of reasoning-tools dedicated to Abstract Argumentation Frameworks. These systems are ArgTools, ASPARTIX, ConArg2, and Dung-O-Matic. They have been tested over three different models of randomly-generated graph models, corresponding to the Erdős-Rényi model, the Kleinberg small-world model, and the scale-free Barabasi-Albert model. This first comparison is useful to study the behaviour of these tools over networks with different topologies (also small-world): we scale the number of arguments to check the limits of today’s systems. Such results can be used to guide further improvements of ConArg2 (our tool), but also different tools.},
	keywords = {SEMANTICS, FRAMEWORKS},
	doi = {10.3233/FI-2015-1254},	
	pages = {263--278}
}

We compare four different implementations of reasoning-tools dedicated to Abstract Argumentation Frameworks. These systems are ArgTools, ASPARTIX, ConArg2, and Dung-O-Matic. They have been tested over three different models of randomly-generated graph models, corresponding to the Erdős-Rényi model, the Kleinberg small-world model, and the scale-free Barabasi-Albert model. This first comparison is useful to study the behaviour of these tools over networks with different topologies (also small-world): we scale the number of arguments to check the limits of today’s systems. Such results can be used to guide further improvements of ConArg2 (our tool), but also different tools.

@conference{
	11391_1357834,
	author = {Bistarelli, Stefano and Rossi, Fabio and Santini, Francesco and Taticchi, Carlo},
	title = {Towards visualising security with arguments},
	year = {2015},
	publisher = {CEUR-WS.org},
	volume = {1459},
	booktitle = {CILC 2015 Italian Conference on Computational Logic},
	abstract = {Argumentation has been proved as a simple yet powerful approach to manage conicts in reasoning with the purpose to find subsets of surviving arguments. Our intent is to exploit such form of resolution to visually support the administration of security in complex systems. For instance, in case threat countermeasures are in conict (also with assets) and only some of them can be selected.},
	url = {http://ceur-ws.org/Vol-1459/paper28.pdf},
	pages = {197--201}
}

Argumentation has been proved as a simple yet powerful approach to manage conicts in reasoning with the purpose to find subsets of surviving arguments. Our intent is to exploit such form of resolution to visually support the administration of security in complex systems. For instance, in case threat countermeasures are in conict (also with assets) and only some of them can be selected.

@misc{
	11391_1357836,
	author = {Bistarelli, Stefano and Formisano, Andrea and Maratea, Marco},
	title = {RCRA 2015
Experimental Evaluation of Algorithms for Solving Problems with Combinatorial Explosion},
	year = {2015},
	volume = {1451},
	url = {http://ceur-ws.org/Vol-1451/proceedings.pdf},
	pages = {1--90}
}

@conference{
	11391_1357792,
	author = {Bistarelli, Stefano and Rossi, Fabio and Santini, Francesco},
	title = {Testing Credulous and Sceptical Acceptance in Small-World Networks},
	year = {2015},
	publisher = {CEUR-WS.org},
	volume = {1451},
	booktitle = {Proceedings of the 22nd RCRA International Workshop on ExperimentalEvaluation of Algorithms for Solving Problems with Combinatorial Explosion2015 (RCRA 2015) A workshop of the XIV International Conferenceof the Italian Association for Artificial Intelligence (AI*IA 2015),Ferrara, Italy, September 22, 2015.},
	abstract = {In this paper we test how efficiently state-of-the art solvers are capable of solving credulous and sceptical argument-acceptance for lower-order extensions. As our benchmark we consider two different random graph-models to obtain random Abstract Argumentation Frameworks with small-world characteristics: Kleinberg andWatt-Strogatz.We test two reasoners, i.e., ConArg2 and dynPARTIX, on such benchmark, by comparing their performance on NP/co-NP-complete decision problems related to argument acceptance in admissible, complete, and stable semantics.},
	url = {http://ceur-ws.org/Vol-1451/paper4.pdf},
	pages = {39--46}
}

In this paper we test how efficiently state-of-the art solvers are capable of solving credulous and sceptical argument-acceptance for lower-order extensions. As our benchmark we consider two different random graph-models to obtain random Abstract Argumentation Frameworks with small-world characteristics: Kleinberg andWatt-Strogatz.We test two reasoners, i.e., ConArg2 and dynPARTIX, on such benchmark, by comparing their performance on NP/co-NP-complete decision problems related to argument acceptance in admissible, complete, and stable semantics.

@conference{
	11391_1329112,
	author = {Benedetti, Irene and Bistarelli, Stefano and Piersanti, Paolo},
	title = {On Relating Voting Systems and Argumentation Frameworks},
	year = {2014},
	publisher = {CEUR-WS},
	volume = {1195},
	booktitle = {Proceedings of the 29th Italian Conference on Computational Logic},
	abstract = {In the modern world formal voting theories are becoming established and can be used to determine if a Voting System (VS) is fair or not in order to preserve democracy. The Argumentation Framework (AF) is based on the exchange
and the evaluation of interacting arguments which may represent information of various kinds. We define a bijective mapping between the two theories and investigate how fairness criteria defined for voting systems can be re-interpreted
inside the Argumentation Frameworks.},
	pages = {309--313}
}

In the modern world formal voting theories are becoming established and can be used to determine if a Voting System (VS) is fair or not in order to preserve democracy. The Argumentation Framework (AF) is based on the exchange and the evaluation of interacting arguments which may represent information of various kinds. We define a bijective mapping between the two theories and investigate how fairness criteria defined for voting systems can be re-interpreted inside the Argumentation Frameworks.

@conference{
	11391_1345379,
	author = {Bistarelli, Stefano and Costantino, Gianpiero and Martinelli, Fabio and Santini, Francesco},
	title = {An Improved Role-Based Access to Android Applications with JCHR},
	year = {2014},
	publisher = {IEEE Computer Society},
	booktitle = {Proceedings 9th International Conference on Availability, Reliability and Security, ARES 2014},
	abstract = {In this paper we show how deductive and abductive reasoning in distributed authorisation can be efficiently ported to Android. Such logical-inference processes prove to be important tools due to the intrinsic autonomic-nature of these mobile devices. Both deduction and abduction are represented by using Constraint Handling Rules (CHR), a high-level declarative constraint programming-language, and implemented in JCHR (CHR embedded into Java). To represent credentials we elaborate on RTW, a weighted Role-based Trust-management family of languages: CHR programs are developed after such languages. In general, having weights associated with credentials leads to a more informative reasoning, for instance, access can be granted only if the total uncertainty is less than 20%.},
	doi = {10.1109/ARES.2014.52},	
	pages = {341--348}
}

In this paper we show how deductive and abductive reasoning in distributed authorisation can be efficiently ported to Android. Such logical-inference processes prove to be important tools due to the intrinsic autonomic-nature of these mobile devices. Both deduction and abduction are represented by using Constraint Handling Rules (CHR), a high-level declarative constraint programming-language, and implemented in JCHR (CHR embedded into Java). To represent credentials we elaborate on RTW, a weighted Role-based Trust-management family of languages: CHR programs are developed after such languages. In general, having weights associated with credentials leads to a more informative reasoning, for instance, access can be granted only if the total uncertainty is less than 20%.

@conference{
	11391_1345400,
	author = {Bistarelli, Stefano and Ceberio, Martine and Henderson, Joel A. and Santini, Francesco},
	title = {Abstract argumentation frameworks to promote fairness and rationality in multi-experts multi-criteria decision making},
	year = {2014},
	publisher = {CEUR-WS.org},
	volume = {1231},
	booktitle = {Proceedings of the 15th Italian Conference on Theoretical ComputerScience, ,},
	url = {http://ceur-ws.org/Vol-1231/short3.pdf},
	pages = {247--257}
}

@article{
	11391_1345351,
	author = {Bistarelli, Stefano and Santini, Francesco},
	title = {A Secure Non-monotonic Soft Concurrent Constraint Language},
	year = {2014},
	journal = {FUNDAMENTA INFORMATICAE},
	volume = {134},
	abstract = {We present a fine-grained security model to enforce the access control on the shared constraint store in Concurrent Constraint Programming (CCP) languages. We show the model for a non-monotonic version of Soft CCP (SCCP), that is an extension of CCP where the constraints have a preference level associated with them. Crisp constraints can be modeled in the same framework as well. In the considered non-monotonic soft version (NmSCCP), it is also possible to remove constraints from the store. The language can be used for coordinating agents on a common store of information that represents the set of shared resources. In such scenarios, it is clearly important to enforce the integrity and confidentiality rights on the resources, in order, for instance, to hide part of the information to some agents, or to prevent an agent to consume too many resources. Finally, we present a bisimulation relation to check equivalence between two programs written in this language.},
	keywords = {ACCESS-CONTROL, COORDINATION},
	url = {http://dx.doi.org/10.3233/FI-2014-1102},
	doi = {10.3233/FI-2014-1102},	
	pages = {261--285}
}

We present a fine-grained security model to enforce the access control on the shared constraint store in Concurrent Constraint Programming (CCP) languages. We show the model for a non-monotonic version of Soft CCP (SCCP), that is an extension of CCP where the constraints have a preference level associated with them. Crisp constraints can be modeled in the same framework as well. In the considered non-monotonic soft version (NmSCCP), it is also possible to remove constraints from the store. The language can be used for coordinating agents on a common store of information that represents the set of shared resources. In such scenarios, it is clearly important to enforce the integrity and confidentiality rights on the resources, in order, for instance, to hide part of the information to some agents, or to prevent an agent to consume too many resources. Finally, we present a bisimulation relation to check equivalence between two programs written in this language.

@conference{
	11391_1345517,
	author = {Bistarelli, Stefano and Rossi, Fabio and Santini, Francesco},
	title = {Benchmarking Hard Problems in Random Abstract AFs: The Stable Semantics},
	year = {2014},
	publisher = {IOS Press},
	volume = {266},
	booktitle = {COMPUTATIONAL MODELS OF ARGUMENT},
	abstract = {In this paper we test four different implementations of reasoning tools dedicated to Abstract Argumentation Frameworks. These systems are ASPARTIX, dynPARTIX, Dung-O-Matic, and ConArg2. The tests are executed over three different models of randomly-generated graphs, i.e., the Erds-Renyi model, the Kleinberg small-world model, and the scale-free Barabasi-Albert model. We compare these four tools with the purpose to test the search of all the possible stable extensions. Then we benchmark dynPARTIX and ConArg2 on the credulous and skeptical acceptance of arguments. Finally, we also evaluate ConArg2 to check the existence of a stable extension.},
	url = {http://dx.doi.org/10.3233/978-1-61499-436-7-153},
	doi = {10.3233/978-1-61499-436-7-153},	
	pages = {153--160}
}

In this paper we test four different implementations of reasoning tools dedicated to Abstract Argumentation Frameworks. These systems are ASPARTIX, dynPARTIX, Dung-O-Matic, and ConArg2. The tests are executed over three different models of randomly-generated graphs, i.e., the Erds-Renyi model, the Kleinberg small-world model, and the scale-free Barabasi-Albert model. We compare these four tools with the purpose to test the search of all the possible stable extensions. Then we benchmark dynPARTIX and ConArg2 on the credulous and skeptical acceptance of arguments. Finally, we also evaluate ConArg2 to check the existence of a stable extension.

@conference{
	11391_1345532,
	author = {Bistarelli, Stefano and Rossi, Fabio and Santini, Francesco},
	title = {A First Comparison of Abstract Argumentation Reasoning-Tools},
	year = {2014},
	publisher = {{IOS} Press},
	volume = {263},
	booktitle = {{ECAI} 2014 - 21st European Conference on Artificial Intelligence,18-22 August 2014, Prague, Czech Republic - Including PrestigiousApplications of Intelligent Systems {(PAIS} 2014)},
	abstract = {We compare three different implementations of reasoning tools dedicated to Abstract Argumentation Frameworks. These systems are ASPARTIX, ConArg2, and Dung-O-Matic. They have been tested over three different random graph-models, corresponding to the Erdös-Rényi model, Kleinberg small-world model, and scale-free Barabasi model.},
	url = {http://dx.doi.org/10.3233/978-1-61499-419-0-969},
	doi = {10.3233/978-1-61499-419-0-969},	
	pages = {969--970}
}

We compare three different implementations of reasoning tools dedicated to Abstract Argumentation Frameworks. These systems are ASPARTIX, ConArg2, and Dung-O-Matic. They have been tested over three different random graph-models, corresponding to the Erdös-Rényi model, Kleinberg small-world model, and scale-free Barabasi model.

@conference{
	11391_1345535,
	author = {Bistarelli, Stefano and Rossi, Fabio and Santini, Francesco},
	title = {Efficient Solution for Credulous/Sceptical Acceptance in Lower-Order Dung's Semantics},
	year = {2014},
	publisher = {IEEE Computer Society},
	booktitle = {26th IEEE International Conference on Tools with Artificial Intelligence, ICTAI 2014},
	abstract = {We provide an extensive testing on how efficiently state-of-the art solvers are capable of solving credulous and sceptical argument-acceptance for lower-order extensions. In fact, as our benchmark we consider three different random graph-models to represent random Abstract Argumentation Frameworks: Barabasi and Erdos-Renyi networks, and, in addition, we also rework balanced trees by randomise their structure, with the purpose to obtain random trees of different height. Therefore, we test two reasoners, i.e., Con Arg2 and dyn PARTIX, on such benchmark, by comparing their performance on NP/co-NP-complete decision problems related to argument acceptance in admissible, complete, and stable semantics.},
	doi = {10.1109/ICTAI.2014.123},	
	pages = {800--804}
}

We provide an extensive testing on how efficiently state-of-the art solvers are capable of solving credulous and sceptical argument-acceptance for lower-order extensions. In fact, as our benchmark we consider three different random graph-models to represent random Abstract Argumentation Frameworks: Barabasi and Erdos-Renyi networks, and, in addition, we also rework balanced trees by randomise their structure, with the purpose to obtain random trees of different height. Therefore, we test two reasoners, i.e., Con Arg2 and dyn PARTIX, on such benchmark, by comparing their performance on NP/co-NP-complete decision problems related to argument acceptance in admissible, complete, and stable semantics.

@conference{
	11391_1345538,
	author = {Bistarelli, Stefano and Santini, Francesco},
	title = {Two trust networks in one: Using bipolar structures to fuse trust and distrust},
	year = {2014},
	publisher = {IEEE Press},
	booktitle = {12th Annual Conference on Privacy, Security and Trust, PST 2014},
	abstract = {In this paper we study weighted trust-networks, where each edge is associated with either a positive or negative score. Hence, we consider a distrust relationship as well, allowing a user to rate poor experiences with other individuals in his web of acquaintances. We propose an algorithm to compose two of such networks in a single one, in order to merge the knowledge obtained in two different communities of individuals (possibly partially-overlapping), through two different trust management-systems. Our algorithm is based on semiring algebraic-structures, in order to have a parametric computational-framework. Such composition can be adopted whenever two trust-based communities (with the same scope) need to be amalgamated: for instance, two competitor-companies that need to unify the trust-based knowledge on their (sub-) suppliers.},
	doi = {10.1109/PST.2014.6890964},	
	pages = {383--390}
}

In this paper we study weighted trust-networks, where each edge is associated with either a positive or negative score. Hence, we consider a distrust relationship as well, allowing a user to rate poor experiences with other individuals in his web of acquaintances. We propose an algorithm to compose two of such networks in a single one, in order to merge the knowledge obtained in two different communities of individuals (possibly partially-overlapping), through two different trust management-systems. Our algorithm is based on semiring algebraic-structures, in order to have a parametric computational-framework. Such composition can be adopted whenever two trust-based communities (with the same scope) need to be amalgamated: for instance, two competitor-companies that need to unify the trust-based knowledge on their (sub-) suppliers.

@misc{
	11391_1345503,
	author = {Bistarelli, Stefano and Formisano, Andrea},
	title = {Proceedings of the 15th Italian Conference on Theoretical Computer
Science, ICTCS2014},
	year = {2014},
	publisher = {CEUR-WS.org},
	volume = {1231},
	url = {http://ceur-ws.org/Vol-1231}
}

@conference{
	11391_1345390,
	author = {Bistarelli, Stefano and Rossi, Fabio and Santini, Francesco},
	title = {Enumerating Extensions on Random Abstract-AFs with ArgTools, Aspartix, ConArg2, and Dung-O-Matic},
	year = {2014},
	publisher = {Springer},
	volume = {8624},
	booktitle = {Proceedings 15th International Workshop on Computational Logic in Multi-Agent Systems, CLIMA 2014},
	doi = {10.1007/978-3-319-09764-0_5},	
	pages = {70--86}
}

@inbook{
	11391_1345404,
	author = {Bistarelli, Stefano and Formisano, Andrea},
	title = {Preface},
	year = {2014},
	publisher = {CEUR-WS.org},
	volume = {1231},
	booktitle = {Proceedings of the 15th Italian Conference on Theoretical ComputerScience, Perugia, Italy, September 17-19, 2014.},
	url = {http://ceur-ws.org/Vol-1231/preface.pdf},
	pages = {i--v}
}

@conference{
	11391_1218491,
	author = {Henderson, Joel and Bistarelli, Stefano and Ceberio, Martine},
	title = {Multi-Experts Multi-Criteria Decision Making},
	year = {2013},
	publisher = {Luigi Pellegrini Editore},
	booktitle = {Proceeding of the international conference «numerical computations: theory and algorithms},
	doi = {10.978.886822/0327},	
}

@article{
	11391_1158897,
	author = {Bistarelli, S. and Faltings, B. and Neagu, N.},
	title = {Interchangeability with thresholds and degradation factors for Soft CSPs},
	year = {2013},
	journal = {ANNALS OF MATHEMATICS AND OF ARTIFICIAL INTELLIGENCE},
	volume = {67},
	abstract = {Substitutability and interchangeability in constraint satisfaction problems (CSPs) have been used as a basis for search heuristics, solution adaptation and abstraction techniques. In this paper, we consider how the same concepts can be extended to soft constraint satisfaction problems (SCSPs). We introduce two notions: threshold α and degradation factor δ for substitutability and interchangeability, (αsubstitutability/interchangeability and δsubstitutability/interchangeabi-lity respectively). We show that they satisfy analogous theorems to the ones already known for hard constraints. In αinterchangeability, values are interchangeable in any solution that is better than a threshold α, thus allowing to disregard differences among solutions that are not sufficiently good anyway. In δinterchangeability, values are interchangeable if their exchange could not degrade the solution by more than a factor of δ. We give efficient algorithms to compute (δ/α)interchangeable sets of values for a large class of SCSPs, and show an example of their application. Through experimental evaluation based on random generated problem we measure first, how often neighborhood interchangeable values are occurring, second, how well they can approximate fully interchangeable ones, and third, how efficient they are when used as preprocessing techniques for branch and bound search.},
	keywords = {Constraint optimization, Constraint satisfaction, Interchangeability, Soft constraints},
	doi = {10.1007/s10472-013-9348-8},	
	pages = {123--163}
}

Substitutability and interchangeability in constraint satisfaction problems (CSPs) have been used as a basis for search heuristics, solution adaptation and abstraction techniques. In this paper, we consider how the same concepts can be extended to soft constraint satisfaction problems (SCSPs). We introduce two notions: threshold α and degradation factor δ for substitutability and interchangeability, (αsubstitutability/interchangeability and δsubstitutability/interchangeabi-lity respectively). We show that they satisfy analogous theorems to the ones already known for hard constraints. In αinterchangeability, values are interchangeable in any solution that is better than a threshold α, thus allowing to disregard differences among solutions that are not sufficiently good anyway. In δinterchangeability, values are interchangeable if their exchange could not degrade the solution by more than a factor of δ. We give efficient algorithms to compute (δ/α)interchangeable sets of values for a large class of SCSPs, and show an example of their application. Through experimental evaluation based on random generated problem we measure first, how often neighborhood interchangeable values are occurring, second, how well they can approximate fully interchangeable ones, and third, how efficient they are when used as preprocessing techniques for branch and bound search.

@misc{
	11391_1158901,
	author = {Bistarelli, Stefano and Monfroy, Eric and O'Sullivan, Barry},
	title = {Proceedings of the 2013 ACM Symposium on Applied Computing - Constraint solving and programming track},
	year = {2013}
}

@article{
	11391_1158898,
	author = {Bistarelli, Stefano and Santini, Francesco},
	title = {Coalitions of Arguments: An Approach with Constraint Programming},
	year = {2013},
	journal = {FUNDAMENTA INFORMATICAE},
	volume = {124},
	abstract = {The aggregation of generic items into coalitions leads to the creation of sets of homogenous entities. In this paper we accomplish this for an input set of arguments, and the result is a partition according to distinct lines of thought, i.e., groups of "coherent" ideas. We extend Dung's Argumentation Framework (AF) in order to deal with coalitions of arguments. The initial set of arguments is partitioned into not-intersected subsets. All the found coalitions show the same property inherited by Dung, e.g., all the coalitions in the partition are admissible (or conflict-free, complete, stable): they are generated according to Dung's principles. Each of these coalitions can be assigned to a different agent. We use Soft Constraint Programming as a formal approach to model and solve such partitions in weighted AFs: semiring algebraic structures can be used to model different optimization criteria for the obtained coalitions. Moreover, we implement and solve the presented problem with JaCoP, a Java constraint solver, and we test the code over a small-world network.},
	keywords = {SMALL-WORLD, FRAMEWORK, NETWORKS, SYSTEMS},
	doi = {10.3233/FI-2013-840},	
	pages = {383--401}
}

The aggregation of generic items into coalitions leads to the creation of sets of homogenous entities. In this paper we accomplish this for an input set of arguments, and the result is a partition according to distinct lines of thought, i.e., groups of "coherent" ideas. We extend Dung's Argumentation Framework (AF) in order to deal with coalitions of arguments. The initial set of arguments is partitioned into not-intersected subsets. All the found coalitions show the same property inherited by Dung, e.g., all the coalitions in the partition are admissible (or conflict-free, complete, stable): they are generated according to Dung's principles. Each of these coalitions can be assigned to a different agent. We use Soft Constraint Programming as a formal approach to model and solve such partitions in weighted AFs: semiring algebraic structures can be used to model different optimization criteria for the obtained coalitions. Moreover, we implement and solve the presented problem with JaCoP, a Java constraint solver, and we test the code over a small-world network.

@conference{
	11391_1158906,
	author = {Bistarelli, Stefano and Rossi, Fabio and Santini, Francesco},
	title = {A First Comparison of Abstract Argumentation Systems: A Computational Perspective},
	year = {2013},
	publisher = {CEUR},
	journal = {CEUR WORKSHOP PROCEEDINGS},
	volume = {1068},
	booktitle = {Proceedings of the 28th Italian Conference on Computational Logic},
	pages = {241--245}
}

@conference{
	11391_1158903,
	author = {Bistarelli, Stefano and Gosti, Giorgio and Santini, Francesco},
	title = {Solving Fuzzy Distributed CSPs: An Approach with Naming Games},
	year = {2013},
	publisher = {Springer-Verlag},
	volume = {7784},
	booktitle = {Declarative Agent Languages and Technologies X - 10th International Workshop, DALT 2012},
	abstract = {Constraint Satisfaction Problems (CSPs) are the formalization of a large range of problems that emerge from computer science. The solving methodology described here is based on Naming Games (NGs). NGs were introduced to represent N agents that have to bootstrap an agreement on a name to give to an object (i.e., a word). In this paper we focus on solving both Fuzzy NGs and Fuzzy Distributed CSPs (Fuzzy DCSPs) with an algorithm inspired by NGs. In this framework, each proposed solution is associated with a preference represented as a fuzzy score. We want the agents to find the solution, which is associated with the highest preference value among all solutions. The two main features that distinguish this methodology from classical Fuzzy DCSPs algorithms are that i) the system can react to small instance changes, and ii) the fact the algorithm does not require a pre-agreed agent/variable ordering.},
	doi = {10.1007/978-3-642-37890-4_7},	
	pages = {116--135}
}

Constraint Satisfaction Problems (CSPs) are the formalization of a large range of problems that emerge from computer science. The solving methodology described here is based on Naming Games (NGs). NGs were introduced to represent N agents that have to bootstrap an agreement on a name to give to an object (i.e., a word). In this paper we focus on solving both Fuzzy NGs and Fuzzy Distributed CSPs (Fuzzy DCSPs) with an algorithm inspired by NGs. In this framework, each proposed solution is associated with a preference represented as a fuzzy score. We want the agents to find the solution, which is associated with the highest preference value among all solutions. The two main features that distinguish this methodology from classical Fuzzy DCSPs algorithms are that i) the system can react to small instance changes, and ii) the fact the algorithm does not require a pre-agreed agent/variable ordering.

@article{
	11391_1002065,
	author = {Bistarelli, Stefano and Martinelli, Fabio and Santini, Francesco},
	title = {A semiring-based framework for the deduction/abduction reasoning in access control with weighted credentials},
	year = {2012},
	journal = {COMPUTERS & MATHEMATICS WITH APPLICATIONS},
	volume = {64},
	abstract = {We present a variant of the Datalog language (we call it Datalog W), which is able to deal with weights on ground facts. The weights are chosen from a semiring algebraic structure. Our goal is to use this language as a semantic foundation for trust-management languages, in order to express trust relationships associated with a preference (e.g., a cost, an uncertainty, a trust or a fuzzy value). We apply Datalog W as the basis to give a uniform semantics to a weighted extension of the RT language family, called RT W. Moreover, we show that we can model the deduction and abduction reasoning with semiring-based soft constraints: deduction can validate or not the access request, while abduction can be used to compute the missing credentials if the access is denied and the level of preference that would grant the access.},
	keywords = {Abduction, Deduction, Role-based Trust-management languages, Soft constraint},
	doi = {10.1016/j.camwa.2011.12.017},	
	pages = {447--462}
}

We present a variant of the Datalog language (we call it Datalog W), which is able to deal with weights on ground facts. The weights are chosen from a semiring algebraic structure. Our goal is to use this language as a semantic foundation for trust-management languages, in order to express trust relationships associated with a preference (e.g., a cost, an uncertainty, a trust or a fuzzy value). We apply Datalog W as the basis to give a uniform semantics to a weighted extension of the RT language family, called RT W. Moreover, we show that we can model the deduction and abduction reasoning with semiring-based soft constraints: deduction can validate or not the access request, while abduction can be used to compute the missing credentials if the access is denied and the level of preference that would grant the access.

@article{
	11391_309893,
	author = {Bistarelli, Stefano and Gadducci, F. and Larrosa, J. and Rollon, E. and Santini, Francesco},
	title = {Local Arc Consistency for Non-Invertible Semirings, with an Application to Multi-Objective Optimization},
	year = {2012},
	journal = {EXPERT SYSTEMS WITH APPLICATIONS},
	volume = {39},
	abstract = {We extend algorithms for local arc consistency proposed in the literature in order to deal with (absorptive) semirings that may not be invertible. As a consequence, these consistency algorithms can be used as a pre-processing procedure in soft Constraint Satisfaction Problems (CSPs) defined over a larger class of semirings, such as those obtained from the Cartesian product of two (or more) semirings. One important instance of this class of semirings is adopted for multi-objective CSPs. First, we show how a semiring can be transformed into a novel one where the + operator is instantiated with the least common divisor (LCD) between the elements of the original semiring. The LCD value corresponds to the amount we can "safely move" from the binary constraint to the unary one in the arc consistency algorithm. We then propose a local arc consistency algorithm which takes advantage of this LCD operator.},
	keywords = {CONSTRAINT SATISFACTION, SOFT CONSTRAINTS, Invertible semiring, Multi-objective, Arc consistency},
	doi = {10.1016/j.eswa.2011.06.062},	
	pages = {1708--1717}
}

We extend algorithms for local arc consistency proposed in the literature in order to deal with (absorptive) semirings that may not be invertible. As a consequence, these consistency algorithms can be used as a pre-processing procedure in soft Constraint Satisfaction Problems (CSPs) defined over a larger class of semirings, such as those obtained from the Cartesian product of two (or more) semirings. One important instance of this class of semirings is adopted for multi-objective CSPs. First, we show how a semiring can be transformed into a novel one where the + operator is instantiated with the least common divisor (LCD) between the elements of the original semiring. The LCD value corresponds to the amount we can "safely move" from the binary constraint to the unary one in the arc consistency algorithm. We then propose a local arc consistency algorithm which takes advantage of this LCD operator.

@article{
	11391_176498,
	author = {Bistarelli, S. and Fabio, Fioravanti and Pamela, Peretti and Francesco, Santini},
	title = {Evaluation of complex security scenarios using defense trees and economic indexes},
	year = {2012},
	journal = {JOURNAL OF EXPERIMENTAL & THEORETICAL ARTIFICIAL INTELLIGENCE},
	volume = {24},
	abstract = {In this article, we present a mixed qualitative and quantitative approach for evaluation of information technology (IT) security investments. For this purpose, we model security scenarios by using defense trees, an extension of attack trees with countermeasures and we use economic quantitative indexes for computing the defender's return on security investment and the attacker's return on attack. We show how our approach can be used to evaluate economic profitability of countermeasures and their deterrent effect on attackers, thus providing decision makers with a useful tool for performing better evaluation of IT security investments during the risk management process.},
	keywords = {security scenarios, defense tree, economic indexes, ROI; ROA},
	doi = {10.1080/13623079.2011.587206},	
	pages = {161--192}
}

In this article, we present a mixed qualitative and quantitative approach for evaluation of information technology (IT) security investments. For this purpose, we model security scenarios by using defense trees, an extension of attack trees with countermeasures and we use economic quantitative indexes for computing the defender's return on security investment and the attacker's return on attack. We show how our approach can be used to evaluate economic profitability of countermeasures and their deterrent effect on attackers, thus providing decision makers with a useful tool for performing better evaluation of IT security investments during the risk management process.

@inbook{
	11391_309493,
	author = {Bistarelli, S. and Martinelli, F. and Roperti, F. and Santini, F.},
	title = {Negotiation on mobile devices using Weighted RTML Credentials},
	year = {2012},
	publisher = {Springer},
	booktitle = {INFORMATION SYSTEMS: CROSSROADS FOR ORGANIZATION, MANAGEMENT, ACCOUNTING AND ENGINEERING},
	abstract = {In this paper we describe an implementation for mobile phones of two important services in logical reasoning, that is deduction and abduction, defined over a set of weighted credentials. The main benefit comes during the process of automated access authorization based on trust: soft constraint operations can be easily adopted to measure the level of trust required for each operation. Moreover, when the level is not sufficient, abduction can be used to compute the missing credentials and the levels that grant the access. We implement a negotiation of credentials between two mobile devices in order to grant the access to the requestor peer, with the use of deduction/abduction services.},
	doi = {10.1007/978-3-7908-2789-7_47},	
	pages = {429--438}
}

In this paper we describe an implementation for mobile phones of two important services in logical reasoning, that is deduction and abduction, defined over a set of weighted credentials. The main benefit comes during the process of automated access authorization based on trust: soft constraint operations can be easily adopted to measure the level of trust required for each operation. Moreover, when the level is not sufficient, abduction can be used to compute the missing credentials and the levels that grant the access. We implement a negotiation of credentials between two mobile devices in order to grant the access to the requestor peer, with the use of deduction/abduction services.

@conference{
	11391_313897,
	author = {Bistarelli, Stefano and Santini, Francesco},
	title = {Modeling and Solving AFs with a Constraint-Based Tool: ConArg},
	year = {2012},
	publisher = {Springer-Verlag},
	volume = {7132},
	booktitle = {Theorie and Applications of Formal Argumentation - First International Workshop, TAFA 2011},
	abstract = {ConArg is a tool based on Constraint Programming which is able to model and solve different problems related to Argumentation Frameworks (AFs). To practically implement the tool, we have used JaCoP, a Java library which provides the user with a Finite Domain Constraint Programming paradigm. Constraint Satisfaction Problems (CSPs) offer a wide number of efficient techniques (as inference and search algorithms) that can tackle the complexity in finding all the possible Dung's conflict-free, admissible, complete and stable extensions in AFs. Moreover, we can use the tool to solve some of the preference-based problems presented in literature. ConArg is able to randomly generate networks with small-world properties in order to find Dung's extensions on such interaction graphs. We present the main features of ConArg and we report the performance in time.},
	doi = {10.1007/978-3-642-29184-5_7},	
	pages = {99--116}
}

ConArg is a tool based on Constraint Programming which is able to model and solve different problems related to Argumentation Frameworks (AFs). To practically implement the tool, we have used JaCoP, a Java library which provides the user with a Finite Domain Constraint Programming paradigm. Constraint Satisfaction Problems (CSPs) offer a wide number of efficient techniques (as inference and search algorithms) that can tackle the complexity in finding all the possible Dung's conflict-free, admissible, complete and stable extensions in AFs. Moreover, we can use the tool to solve some of the preference-based problems presented in literature. ConArg is able to randomly generate networks with small-world properties in order to find Dung's extensions on such interaction graphs. We present the main features of ConArg and we report the performance in time.

@misc{
	11391_310293,
	author = {Bistarelli, S. and Monfroi, E. and O'Sullivan, B.},
	title = {Proceedings of the 2012 ACM Symposium on Applied Computing - Constraint solving and programming track},
	year = {2012},
	publisher = {ACM}
}

@conference{
	11391_313896,
	author = {Bistarelli, S. and Paola, Campli and Santini, F.},
	title = {A Secure Coordination of Agents with Nonmonotonic Soft Concurrent Constraint Programming},
	year = {2012},
	publisher = {ACM Special Interest Group on Applied Computing (SIGAPP),Provincia Autonoma di Trento,Riva del Garda Congressi,COSBI},
	booktitle = {Proceedings of the ACM Symposium on Applied Computing, SAC 2012},
	abstract = {We present a fine-grained security model to enforce the access control on the constraint store in Concurrent Constraint Programming (CCP) languages. We show the model for a nonmonotonic version of Soft CCP (SCCP), that is an extension of CCP which deals with soft constraints, which are constraints that have a preference level associated to them. In the considered nomonotonic version (NMSCCP), the language is equipped with actions that can also remove constraints from the store. The language can be used for coordinating the agents on a common store of information. Clearly, in such scenario, is important to enhance the operations that the agents may perform with security and privacy, in order to limit their behavior, e.g., to hide some information or to prevent an agent to consume too many resources},
	doi = {10.1145/2245276.2232023},	
	pages = {1551--1553}
}

We present a fine-grained security model to enforce the access control on the constraint store in Concurrent Constraint Programming (CCP) languages. We show the model for a nonmonotonic version of Soft CCP (SCCP), that is an extension of CCP which deals with soft constraints, which are constraints that have a preference level associated to them. In the considered nomonotonic version (NMSCCP), the language is equipped with actions that can also remove constraints from the store. The language can be used for coordinating the agents on a common store of information. Clearly, in such scenario, is important to enhance the operations that the agents may perform with security and privacy, in order to limit their behavior, e.g., to hide some information or to prevent an agent to consume too many resources

@misc{
	11391_1039272,
	author = {Agostiniani, L. and Bakkum, G. C. L. M. and Bistarelli, S. and Calderini, A. and Massarelli, R. and Meiser, G.},
	title = {CELIA. Corpus Elettronico delle Lingue dell'Italia Antica},
	year = {2012}
}

@conference{
	11391_1158902,
	author = {Bistarelli, Stefano and Santini, Francesco},
	title = {ConArg: Argumentation with Constraints},
	year = {2012},
	publisher = {CEUR Workshop Proceedings},
	volume = {918},
	booktitle = {Proceedings of the First International Conference on Agreement Technologies, AT 2012},
	pages = {197--198}
}

@conference{
	11391_1158899,
	author = {Arbab, Farhad and Santini, Francesco and Bistarelli, Stefano and Pirolandi, Daniele},
	title = {Towards a similarity-based web service discovery through soft constraint satisfaction problems},
	year = {2012},
	publisher = {ACM},
	booktitle = {Proceedings of the 2nd International Workshop on Semantic Search over the Web - SSW '12},
	abstract = {In this paper, we focus on the discovery process of Web Services (WSs) by basing the search on the similarities among the service requirements and candidate search results, in order to cope with over-constrained queries or to find satisfactory alternatives for user requirements. This discovery process needs to involve the so-called Soft Constraint Satisfaction Problems (SCSPs). First we represent both WSs and the search query of the user as Rooted Trees, i.e., a particular form of Conceptual Graphs. Then, we find a homomorphism between these two trees as a solution of an SCSP. The main contribution of this paper is the enhanced expressiveness offered by this "softness": in over-constrained scenarios, when a user query cannot be satisfied, classical crisp constraints (i.e., CSP) are not expressive enough to find "close" solutions to meet the users' needs.},
	doi = {10.1145/2494068.2494070},	
	pages = {1--8}
}

In this paper, we focus on the discovery process of Web Services (WSs) by basing the search on the similarities among the service requirements and candidate search results, in order to cope with over-constrained queries or to find satisfactory alternatives for user requirements. This discovery process needs to involve the so-called Soft Constraint Satisfaction Problems (SCSPs). First we represent both WSs and the search query of the user as Rooted Trees, i.e., a particular form of Conceptual Graphs. Then, we find a homomorphism between these two trees as a solution of an SCSP. The main contribution of this paper is the enhanced expressiveness offered by this "softness": in over-constrained scenarios, when a user query cannot be satisfied, classical crisp constraints (i.e., CSP) are not expressive enough to find "close" solutions to meet the users' needs.

@conference{
	11391_925727,
	author = {Bistarelli, Stefano and Santini, Francesco},
	title = {Securely Accessing Shared Resources with Concurrent Constraint Programming},
	year = {2012},
	publisher = {Springer-Verlag},
	volume = {7504},
	booktitle = {10th International Conference on Software Engineering and Formal Methods (SEFM 2012)},
	abstract = {We present a fine-grained security model to enforce the access control on the shared constraint store in Concurrent Constraint Programming (CCP) languages. We show the model for a nonmonotonic version of Soft CCP (SCCP), that is an extension of CCP where the constraints have a preference level associated with them. Crisp constraints can be modeled in the same framework as well. In the considered nonmonotonic soft version (NmSCCP), it is also possible to remove constraints from the store. The language can be used for coordinating agents on a common store of information that represents the set of shared resources. In such scenarios, it is clearly important to enforce the integrity and confidentiality rights on the resources, in order, for instance, to hide part of the information to some agents, or to prevent an agent to consume too many resources},
	doi = {10.1007/978-3-642-33826-7_21},	
	pages = {308--322}
}

We present a fine-grained security model to enforce the access control on the shared constraint store in Concurrent Constraint Programming (CCP) languages. We show the model for a nonmonotonic version of Soft CCP (SCCP), that is an extension of CCP where the constraints have a preference level associated with them. Crisp constraints can be modeled in the same framework as well. In the considered nonmonotonic soft version (NmSCCP), it is also possible to remove constraints from the store. The language can be used for coordinating agents on a common store of information that represents the set of shared resources. In such scenarios, it is clearly important to enforce the integrity and confidentiality rights on the resources, in order, for instance, to hide part of the information to some agents, or to prevent an agent to consume too many resources

@conference{
	11391_1158900,
	author = {Bistarelli, Stefano and Santini, Francesco},
	title = {Semiring-based constraint models and frameworks for security-related scenarios},
	year = {2012},
	publisher = {IEEE},
	booktitle = {2012 7th International Conference on Risks and Security of Internet and Systems (CRiSIS)},
	abstract = {Semiring-based constraint models and frameworks have been extensively used in literature to optimize different security-related metrics, in order to represent trust scores, levels of security and, in general, quantitative information on shared resources to be securely managed. In this tutorial, we summarize four approaches that show an application of these formal models to different security-related problems, as Access Control List-like rights, policy-based access with weighted credentials, propagation of trust on trust-networks, and the cascade vulnerability problem.},
	doi = {10.1109/CRISIS.2012.6378958},	
	pages = {1--4}
}

Semiring-based constraint models and frameworks have been extensively used in literature to optimize different security-related metrics, in order to represent trust scores, levels of security and, in general, quantitative information on shared resources to be securely managed. In this tutorial, we summarize four approaches that show an application of these formal models to different security-related problems, as Access Control List-like rights, policy-based access with weighted credentials, propagation of trust on trust-networks, and the cascade vulnerability problem.

@conference{
	11391_143643,
	author = {Foley, S. N. and Bella, G. and Bistarelli, Stefano},
	title = {Security Protocol Deployment Risk},
	year = {2011},
	publisher = {Springer-Verlag},
	volume = {6615},
	booktitle = {Proceeding Security'08 Proceedings of the 16th International conference on Security protocols},
	abstract = {Security protocol participants are software and/or hardware agents that are - as with any system - potentially vulnerable to failure. Protocol analysis should extend not just to an analysis of the protocol specification, but also to its implementation and configuration in its target environment. However, an in-depth formal analysis that considers the behaviour and interaction of all components in their environment is not feasible in practice. This paper considers the analysis of protocol deployment rather than implementation. Instead of concentrating on detailed semantics and formal verification of the protocol and implementation, we are concerned more with with the ability to trace, at a practical level of abstraction, how the protocol deployment, that is, the configuration of the protocol components, relate to each other and the overall protocol goals. We believe that a complete security verification of a system is not currently achievable in practice and seek some degree of useful feedback from an analysis that a particular protocol deployment is reasonable},
	doi = {10.1007/978-3-642-22137-8_3},	
	pages = {12--20}
}

Security protocol participants are software and/or hardware agents that are - as with any system - potentially vulnerable to failure. Protocol analysis should extend not just to an analysis of the protocol specification, but also to its implementation and configuration in its target environment. However, an in-depth formal analysis that considers the behaviour and interaction of all components in their environment is not feasible in practice. This paper considers the analysis of protocol deployment rather than implementation. Instead of concentrating on detailed semantics and formal verification of the protocol and implementation, we are concerned more with with the ability to trace, at a practical level of abstraction, how the protocol deployment, that is, the configuration of the protocol components, relate to each other and the overall protocol goals. We believe that a complete security verification of a system is not currently achievable in practice and seek some degree of useful feedback from an analysis that a particular protocol deployment is reasonable

@misc{
	11391_166444,
	author = {Bistarelli, Stefano and Monfroy, Eric and O'Sullivan, Barry},
	title = {Proceedings of the 2011 ACM Symposium on Applied Computing - Constraint solving and programming track},
	year = {2011},
	publisher = {ACM}
}

@conference{
	11391_309093,
	author = {Bistarelli, Stefano and Gosti, Giorgio and Santini, Francesco},
	title = {Solving Fuzzy DCSPs with Naming Games},
	year = {2011},
	publisher = {IEEE},
	booktitle = {23rd IEEE International Conference on Tools with Artificial Intelligence},
	abstract = {In this paper we focus on solving Fuzzy Distributed Constraint Satisfaction Problems (Fuzzy DCSPs) with an algorithm for Naming Games (NGs): each word on which the agents have to agree on is associated with a preference represented as a fuzzy score. The solution is the agreed word associated with the highest preference value. The two main features that distinguish this methodology from Fuzzy DCSPs methods are that the system can react to small instance changes and and it does not require pre-agreed agent/variable ordering.},
	doi = {10.1109/ICTAI.2011.159},	
	pages = {605--612}
}

In this paper we focus on solving Fuzzy Distributed Constraint Satisfaction Problems (Fuzzy DCSPs) with an algorithm for Naming Games (NGs): each word on which the agents have to agree on is associated with a preference represented as a fuzzy score. The solution is the agreed word associated with the highest preference value. The two main features that distinguish this methodology from Fuzzy DCSPs methods are that the system can react to small instance changes and and it does not require pre-agreed agent/variable ordering.

@conference{
	11391_166441,
	author = {Bistarelli, Stefano and Pirolandi, Daniele and Santini, Francesco},
	title = {Solving Weighted Argumentation Frameworks with Soft Constraints},
	year = {2011},
	publisher = {Springer-Verlag},
	volume = {6384/2011},
	booktitle = {Javier Larrosa, Barry O'Sullivan},
	abstract = {We suggest soft constraints as a mean to parametrically represent and solve "weighted" Argumentation problems: different kinds of preference levels related to arguments, e.g. a score representing a "fuzziness", a "cost" or a probability level of each argument, can be represented by choosing different semiring algebraic structures. The novel idea is to provide a common computational and quantitative framework where the computation of the classical Dung's extensions, e.g. the admissible extension, has an associated score representing "how much good" the set is. Preference values associated to arguments are clearly more informative and can be used to prefer a given set of arguments over others with the same characteristics (e.g. admissibility). Moreover, we propose a mapping from weighted Argumentation Frameworks to Soft Constraint Satisfaction Problems (SCSPs); with this mapping we can compute Dung semantics (e.g. admissible and stable) by solving the related SCSP. To implement this mapping we use JaCoP, a Java constraint solver.},
	doi = {10.1007/978-3-642-19486-3_1},	
	pages = {1--18}
}

We suggest soft constraints as a mean to parametrically represent and solve "weighted" Argumentation problems: different kinds of preference levels related to arguments, e.g. a score representing a "fuzziness", a "cost" or a probability level of each argument, can be represented by choosing different semiring algebraic structures. The novel idea is to provide a common computational and quantitative framework where the computation of the classical Dung's extensions, e.g. the admissible extension, has an associated score representing "how much good" the set is. Preference values associated to arguments are clearly more informative and can be used to prefer a given set of arguments over others with the same characteristics (e.g. admissibility). Moreover, we propose a mapping from weighted Argumentation Frameworks to Soft Constraint Satisfaction Problems (SCSPs); with this mapping we can compute Dung semantics (e.g. admissible and stable) by solving the related SCSP. To implement this mapping we use JaCoP, a Java constraint solver.

@conference{
	11391_166438,
	author = {Bistarelli, Stefano. and Campli, P. and Santini, Francesco},
	title = {Finding Partitions of Arguments with Dung’s Properties via SCSPs},
	year = {2011},
	publisher = {ACM Special Interest Group on Applied Computing (SIGAPP),Tunghai University,Taiwan Ministry of Education,Taiwan Bureau of Foreign Trade,Taiwan National Science Council (NSC)},
	booktitle = {Proceedings of the ACM Symposium on Applied Computing},
	abstract = {Forming coalition structures allows agents to join their forces with the aim to achieve a common task. We suggest it would be interesting to look for homogeneous groups which follow distinct lines of thought. For this reason, we extend the Dung Argumentation Framework in order to deal with coalitions of arguments. The initial set of arguments is partitioned into subsets (or coalitions). Each coalition represents a different line of thought, but all the found coalitions show the same property inherited by Dung, e.g. all the coalitions in the partition are admissible (or conflict-free, complete, stable). Some problems in weighted argumentation are NP complete; we use (soft) constraints as a formal approach to reason about coalitions and to model all these problems in the same framework. Semiring algebraic structures can be used to model different optimization criteria for the obtained coalitions. To implement this mapping and practically find its solutions we use JaCoP, a Java constraint solver, and we test the code over a small-world network.},
	doi = {10.1145/1982185.1982384},	
	pages = {913--919}
}

Forming coalition structures allows agents to join their forces with the aim to achieve a common task. We suggest it would be interesting to look for homogeneous groups which follow distinct lines of thought. For this reason, we extend the Dung Argumentation Framework in order to deal with coalitions of arguments. The initial set of arguments is partitioned into subsets (or coalitions). Each coalition represents a different line of thought, but all the found coalitions show the same property inherited by Dung, e.g. all the coalitions in the partition are admissible (or conflict-free, complete, stable). Some problems in weighted argumentation are NP complete; we use (soft) constraints as a formal approach to reason about coalitions and to model all these problems in the same framework. Semiring algebraic structures can be used to model different optimization criteria for the obtained coalitions. To implement this mapping and practically find its solutions we use JaCoP, a Java constraint solver, and we test the code over a small-world network.

@article{
	11391_166442,
	author = {Bistarelli, S. and Pini, M. S. and Rossi, F. and Venable, K. B.},
	title = {Uncertainty in Bipolar Preference Problems},
	year = {2011},
	journal = {JOURNAL OF EXPERIMENTAL & THEORETICAL ARTIFICIAL INTELLIGENCE},
	volume = {23},
	abstract = {Preferences and uncertainty are common in many real-life problems. In this article, we focus on bipolar preferences and uncertainty modelled via uncontrollable variables, and we assume that uncontrollable variables are specified by possibility distributions over their domains. To tackle such problems, we concentrate on uncertain bipolar problems with totally ordered preferences, and we eliminate the uncertain part of the problem, while making sure that some desirable properties hold about the robustness of the problem and its relationship with the preference of the optimal solutions. We also consider several semantics to order the solutions according to different attitudes with respect to the notions of preference and robustness.},
	keywords = {Soft constraints, Preferences, Uncertainty, Possibility theory, Positive and negative judgements},
	doi = {10.1080/0952813X.2010.524288},	
	pages = {545--575}
}

Preferences and uncertainty are common in many real-life problems. In this article, we focus on bipolar preferences and uncertainty modelled via uncontrollable variables, and we assume that uncontrollable variables are specified by possibility distributions over their domains. To tackle such problems, we concentrate on uncertain bipolar problems with totally ordered preferences, and we eliminate the uncertain part of the problem, while making sure that some desirable properties hold about the robustness of the problem and its relationship with the preference of the optimal solutions. We also consider several semantics to order the solutions according to different attitudes with respect to the notions of preference and robustness.

@conference{
	11391_309293,
	author = {Bistarelli, Stefano and Santini, Francesco},
	title = {ConArg: A Constraint-based Computational Framework for Argumentation Systems},
	year = {2011},
	publisher = {IEEE},
	booktitle = {Proceedings - International Conference on Tools with Artificial Intelligence, ICTAI},
	abstract = {We propose ConArg, a tool based on Constraint Programming, to model and solve various problems related to the Argumentation research field. Constraint Satisfaction Problems (CSPs) offer a wide number of efficient techniques (as inference and search algorithms) that can tackle the complexity in finding all the possible Dung's conflict-free, admissible, complete, stable, preferred and grounded extensions in Argumentation Frameworks. Moreover, we can use the tool to solve some computationally hard problems presented in [1]. To implement ConArg, we have used JaCoP, a Java library which provides the user with a Finite Domain Constraint Programming paradigm, to model and solve these two problems. ConArg is able to randomly generate two different kinds of small-world networks in order to find Dung's extensions on such interaction graphs. We present the main features of ConArg and the reported performance in time.},
	doi = {10.1109/ICTAI.2011.96},	
	pages = {605--612}
}

We propose ConArg, a tool based on Constraint Programming, to model and solve various problems related to the Argumentation research field. Constraint Satisfaction Problems (CSPs) offer a wide number of efficient techniques (as inference and search algorithms) that can tackle the complexity in finding all the possible Dung's conflict-free, admissible, complete, stable, preferred and grounded extensions in Argumentation Frameworks. Moreover, we can use the tool to solve some computationally hard problems presented in [1]. To implement ConArg, we have used JaCoP, a Java library which provides the user with a Finite Domain Constraint Programming paradigm, to model and solve these two problems. ConArg is able to randomly generate two different kinds of small-world networks in order to find Dung's extensions on such interaction graphs. We present the main features of ConArg and the reported performance in time.

@article{
	11391_309693,
	author = {Bistarelli, S. and Santini, F.},
	title = {A Nonmonotonic Soft Concurrent Constraint Language to Model the negotiation Process},
	year = {2011},
	journal = {FUNDAMENTA INFORMATICAE},
	volume = {111},
	abstract = {We present an extension of the Soft Concurrent Constraint language that allows the nonmonotonic evolution of the constraint store. To accomplish this, we introduce some new operations: retract (c) reduces the current store by c, update(X) (c) transactionally relaxes all the constraints of the store that deal with the variables in the set X, and then adds a constraint c; nask (c) tests if c is not entailed by the store. The new retraction operators also permit to reason about Belief Revision, i.e. the process of changing beliefs to take into account a new piece of information. We present this framework as a possible solution to the negotiation of resources (e. g. web services and network resource allocation) that need a given Quality of Service (QoS). For this reason we also show the the new operators of the language satisfy the Belief Revision postulates [20], which can be used in the negotiation process. The QoS requirements (expressed as semiring levels) of all the parties should converge on a formal agreement through a negotiation process, which specifies the contract that must be enforced.},
	keywords = {Soft Constraint, Constraint, Concurrent Programming, Nonmonotonicity,Belief Revision, Quality of Service, Negotiation},
	doi = {10.3233/FI-2011-563},	
	pages = {257--279}
}

We present an extension of the Soft Concurrent Constraint language that allows the nonmonotonic evolution of the constraint store. To accomplish this, we introduce some new operations: retract (c) reduces the current store by c, update(X) (c) transactionally relaxes all the constraints of the store that deal with the variables in the set X, and then adds a constraint c; nask (c) tests if c is not entailed by the store. The new retraction operators also permit to reason about Belief Revision, i.e. the process of changing beliefs to take into account a new piece of information. We present this framework as a possible solution to the negotiation of resources (e. g. web services and network resource allocation) that need a given Quality of Service (QoS). For this reason we also show the the new operators of the language satisfy the Belief Revision postulates [20], which can be used in the negotiation process. The QoS requirements (expressed as semiring levels) of all the parties should converge on a formal agreement through a negotiation process, which specifies the contract that must be enforced.

@conference{
	11391_1158905,
	author = {Bistarelli, Stefano and Campli, Paola and Santini, Francesco},
	title = {Finding Partitions of Arguments with Dung's Properties via SCSPs},
	year = {2011},
	publisher = {CEUR Workshop Proceedings},
	volume = {810},
	booktitle = {CEUR Workshop Proceedings - 26th Italian Conference on Computational Logic, CILC 2011},
	abstract = {Forming coalition structures allows agents to join their forces to achieve a common task. We suggest it would be interesting to look for homogeneous groups which follow distinct lines of thought. For this reason, we extend the Dung Argumentation Framework in order to deal with coalitions of arguments. The initial set of arguments is partitioned into subsets (or coalitions). Each coalition represents a different line of thought, but all the found coalitions show the same property inherited by Dung, e.g. all the coalitions in the partition are admissible (or conflict-free, complete, stable). Some problems in weighted argumentation are NP complete; we use (soft) constraints as a formal approach to reason about coalitions and to model all these problems in the same framework. Semiring algebraic structures can be used to model different optimization criteria for the obtained coalitions. To implement this mapping and practically find its solutions we use JaCoP, a Java constraint solver, and we test the code over a small-world network.},
	pages = {199--213}
}

Forming coalition structures allows agents to join their forces to achieve a common task. We suggest it would be interesting to look for homogeneous groups which follow distinct lines of thought. For this reason, we extend the Dung Argumentation Framework in order to deal with coalitions of arguments. The initial set of arguments is partitioned into subsets (or coalitions). Each coalition represents a different line of thought, but all the found coalitions show the same property inherited by Dung, e.g. all the coalitions in the partition are admissible (or conflict-free, complete, stable). Some problems in weighted argumentation are NP complete; we use (soft) constraints as a formal approach to reason about coalitions and to model all these problems in the same framework. Semiring algebraic structures can be used to model different optimization criteria for the obtained coalitions. To implement this mapping and practically find its solutions we use JaCoP, a Java constraint solver, and we test the code over a small-world network.

@article{
	11391_121123,
	author = {Bistarelli, Stefano and Montanari, Ugo and Rossi, Francesca and Santini, Francesco},
	title = {Unicast and Multicast QoS Routing with Soft Constraint Logic Programming},
	year = {2010},
	journal = {ACM TRANSACTIONS ON COMPUTATIONAL LOGIC},
	volume = {12},
	abstract = {We present a formal model to represent and solve the unicast/multicast routing problem in networks with quality-of-service (QoS) requirements. To attain this, first we translate the network adapting it to a weighted graph (unicast) or and-or graph (multicast), where the weight on a connector corresponds to the multidimensional cost of sending a packet on the related network link: each component of the weights vector represents a different QoS metric value (e.g., bandwidth). The second step consists in writing this graph as a program in soft-constraint logic programming (SCLP): the engine of this framework is then able to find the best paths/trees by optimizing their costs and solving the constraints imposed on them (e.g. delay ≤ 40 ms), thus finding a solution to QoS routing problems. C-semiring structures are a convenient tool to model QoS metrics. At last, we provide an implementation of the framework over scale-free networks and we suggest how the performance can be improved. The article highlights the expressivity of SCLP.},
	keywords = {Constraints; soft constraints, Preferences, Quality of Service (QoS), Routing, Constraint logic programming (CLP), Soft constraint},
	doi = {10.1145/1838552.1838557},	
}

We present a formal model to represent and solve the unicast/multicast routing problem in networks with quality-of-service (QoS) requirements. To attain this, first we translate the network adapting it to a weighted graph (unicast) or and-or graph (multicast), where the weight on a connector corresponds to the multidimensional cost of sending a packet on the related network link: each component of the weights vector represents a different QoS metric value (e.g., bandwidth). The second step consists in writing this graph as a program in soft-constraint logic programming (SCLP): the engine of this framework is then able to find the best paths/trees by optimizing their costs and solving the constraints imposed on them (e.g. delay ≤ 40 ms), thus finding a solution to QoS routing problems. C-semiring structures are a convenient tool to model QoS metrics. At last, we provide an implementation of the framework over scale-free networks and we suggest how the performance can be improved. The article highlights the expressivity of SCLP.

@article{
	11391_121120,
	author = {Bistarelli, Stefano and Pini, MARIA SILVIA and Rossi, Francesca and Venable, K. BRENT},
	title = {From soft constraints to bipolar preferences: modelling framework and solving issues},
	year = {2010},
	journal = {JOURNAL OF EXPERIMENTAL & THEORETICAL ARTIFICIAL INTELLIGENCE},
	volume = {22},
	abstract = {Real-life problems present several kinds of preferences. We focus on problems with both positive and negative preferences, which we call bipolar preference problems. Although seemingly specular notions, these two kinds of preferences should be dealt with differently to obtain the desired natural behaviour. We technically address this by generalising the soft constraint formalism, which is able to model problems with one kind of preference. We show that soft constraints model only negative preferences, and we add to them a new mathematical structure which allows to handle positive preferences as well. We also address the issue of the compensation between positive and negative preferences, studying the properties of this operation. Finally, we extend the notion of arc consistency to bipolar problems, and we show how branch and bound (with or without constraint propagation) can be easily adapted to solve such problems.},
	keywords = {Soft constraints, Preferences, Negative and positive judgements},
	doi = {10.1080/09528130903010212},	
	pages = {135--158}
}

Real-life problems present several kinds of preferences. We focus on problems with both positive and negative preferences, which we call bipolar preference problems. Although seemingly specular notions, these two kinds of preferences should be dealt with differently to obtain the desired natural behaviour. We technically address this by generalising the soft constraint formalism, which is able to model problems with one kind of preference. We show that soft constraints model only negative preferences, and we add to them a new mathematical structure which allows to handle positive preferences as well. We also address the issue of the compensation between positive and negative preferences, studying the properties of this operation. Finally, we extend the notion of arc consistency to bipolar problems, and we show how branch and bound (with or without constraint propagation) can be easily adapted to solve such problems.

@article{
	11391_121124,
	author = {Bistarelli, Stefano and Foley, Simon N. and O'Sullivan, Barry and Santini, Francesco},
	title = {Semiring-based Frameworks for Trust Propagation in Small-World Networks and Coalition Formation Criteria},
	year = {2010},
	journal = {SECURITY AND COMMUNICATION NETWORKS},
	volume = {3},
	abstract = {Multitrust provides a flexible approach to encoding trust metrics whereby definitions for trust propagation and aggregation are specified in terms of a semiring. Determining the degree of trust between principals across a trust network (TN) is, in turn, programmed as a (semiring-based) soft-constraint satisfaction problem. In this paper, we consider the use of semiring-based metrics in reasoning about trust between coalition-forming principals. The configurable nature of multitrust makes it well-suited to modeling trust within coalitions: whether adding more principals to a coalition increases trust or decreases trust is captured by the definition of trust aggregation within the semiring.},
	keywords = {And-or graphs, Soft constraint logic programming, Trust network, Trust propagation},
	doi = {10.1002/sec.252},	
	pages = {595--610}
}

Multitrust provides a flexible approach to encoding trust metrics whereby definitions for trust propagation and aggregation are specified in terms of a semiring. Determining the degree of trust between principals across a trust network (TN) is, in turn, programmed as a (semiring-based) soft-constraint satisfaction problem. In this paper, we consider the use of semiring-based metrics in reasoning about trust between coalition-forming principals. The configurable nature of multitrust makes it well-suited to modeling trust within coalitions: whether adding more principals to a coalition increases trust or decreases trust is captured by the definition of trust aggregation within the semiring.

@conference{
	11391_166440,
	author = {Bistarelli, Stefano and Martinelli, Fabio and Santini, Francesco},
	title = {A Formal Framework for Trust Policy Negotiation in Autonomic Systems: Abduction with Soft Constraints},
	year = {2010},
	publisher = {Springer},
	journal = {LECTURE NOTES IN COMPUTER SCIENCE},
	volume = {6407},
	booktitle = {Autonomic and Trusted Computing, 7th International Conference, ATC 2010.},
	pages = {268--282}
}

@conference{
	11391_166439,
	author = {Bistarelli, Stefano and Gadducci, Fabio and Larrosa, Javier and Rollon, Emma and Santini, Francesco},
	title = {Extending Soft Arc Consistency to Non-Invertible Semirings},
	year = {2010},
	publisher = {Springer},
	volume = {6437},
	booktitle = {Advances in Artificial Intelligence - 9th Mexican International Conference on Artificial Intelligence, MICAI 2010},
	abstract = {We extend algorithms for arc consistency proposed in the literature in order to deal with (absorptive) semirings that are not invertible. As a consequence, these consistency algorithms can be used as a pre-processing procedure in soft Constraint Satisfaction Problems (CSPs) defined over a larger class of semirings: among other instances, for those semirings obtained as the cartesian product of any family of semirings. The main application is that the new arc consistency algorithm can be used for multi-criteria soft CSPs. To reach this objective, we first show that any semiring can be transformed into a new one where the + operator is instantiated with the Least Common Divisor (LCD) between the elements of the original semiring. The LCD value corresponds to the amount we can “safely move” from the binary constraint to the unary one in the arc consistency algorithm (when the × operator of the semiring is not idempotent). We then propose an arc consistency algorithm which takes advantage of this LCD operator.},
	doi = {10.1007/978-3-642-16761-4_34},	
	pages = {386--398}
}

We extend algorithms for arc consistency proposed in the literature in order to deal with (absorptive) semirings that are not invertible. As a consequence, these consistency algorithms can be used as a pre-processing procedure in soft Constraint Satisfaction Problems (CSPs) defined over a larger class of semirings: among other instances, for those semirings obtained as the cartesian product of any family of semirings. The main application is that the new arc consistency algorithm can be used for multi-criteria soft CSPs. To reach this objective, we first show that any semiring can be transformed into a new one where the + operator is instantiated with the Least Common Divisor (LCD) between the elements of the original semiring. The LCD value corresponds to the amount we can “safely move” from the binary constraint to the unary one in the arc consistency algorithm (when the × operator of the semiring is not idempotent). We then propose an arc consistency algorithm which takes advantage of this LCD operator.

@misc{
	11391_166443,
	author = {Bistarelli, Stefano and Monfroy, Eric and O'Sullivan, Barry},
	title = {Proceedings of the 2010 ACM Symposium on Applied Computing - Constraint solving and programming track},
	year = {2010}
}

@article{
	11391_166445,
	author = {Bistarelli, S. and Gosti, G.},
	title = {Solving Distributed CSPs Probabilistically},
	year = {2010},
	journal = {FUNDAMENTA INFORMATICAE},
	volume = {105},
	abstract = {Constraint solving problems (CSPs) are the formalization of a large range of problems that emerge fromcomputer science. The solving methodology described here is based on the naming game. The two main features that distinguish this methodology from most distributed constraint solving problem (DCSPs) methods are: the system can react to small instance changes, and it does not require pre-agreed agent/variable ordering. The naming game was introduced to represent N agents that have to bootstrap an agreement on a name to give to an object. The agents do not have a hierarchy, and use a minimal protocol. Still they converge to a consistent state by using a distributed strategy. For this reason, the naming game can be used to untangle DCSPs. It was shown that a distributed system of uniform finite state machines does not solve the ring ordering problem in all the algorithm executions. Our algorithm is a distributed uniform system of agents able to perform random decisions when presented with equivalent alternatives. We show that this algorithm solves the ring ordering problem with a probability one.},
	keywords = {NAMING GAMES, NETWORK,  LANGUAGE},
	doi = {10.3233/FI-2010-358},	
	pages = {57--78}
}

Constraint solving problems (CSPs) are the formalization of a large range of problems that emerge fromcomputer science. The solving methodology described here is based on the naming game. The two main features that distinguish this methodology from most distributed constraint solving problem (DCSPs) methods are: the system can react to small instance changes, and it does not require pre-agreed agent/variable ordering. The naming game was introduced to represent N agents that have to bootstrap an agreement on a name to give to an object. The agents do not have a hierarchy, and use a minimal protocol. Still they converge to a consistent state by using a distributed strategy. For this reason, the naming game can be used to untangle DCSPs. It was shown that a distributed system of uniform finite state machines does not solve the ring ordering problem in all the algorithm executions. Our algorithm is a distributed uniform system of agents able to perform random decisions when presented with equivalent alternatives. We show that this algorithm solves the ring ordering problem with a probability one.

@conference{
	11391_170515,
	author = {Bistarelli, S. and Campli, P. and Santini, F.},
	title = {Finding Partitions of Arguments with Dung’s Properties via SCSPs},
	year = {2010},
	booktitle = {Proceedings of the Eleventh AI*IA Symposium on Artificial Intelligence},
	pages = {201--208}
}

@conference{
	11391_143885,
	author = {Bistarelli, Stefano and Santini, Francesco},
	title = {A Common Computational Framework for Semiring-based Argumentation Systems},
	year = {2010},
	publisher = {IOS Press},
	volume = {215},
	booktitle = {ECAI 2010 - 19th European Conference on Artificial Intelligence},
	abstract = {We suggest semirings as a mean to parametrically represent "weighted" Argumentation frameworks (AF): different kinds of preference levels related to arguments, e.g. a score representing a "fuzziness", a "cost" or a probability level of each argument, can be represented by choosing different semirings. The novel idea is to provide a common computational and quantitative framework where attacks (and/or supports) have an associated weight and, consequently, also the computation of the classical Dung's semantics has an associated weight representing how much inconsistency we tolerate in the solution. The proposed semiring-based AF is then casted into a Soft Constraint Satisfaction Problem. Adding suitable sets of constraints permits to characterize the solution of the soft CSP as the desired Dung semantics. This allows for the application of the several solution techniques developed for Soft CSPs to AFs.},
	doi = {10.3233/978-1-60750-606-5-131},	
	pages = {131--136}
}

We suggest semirings as a mean to parametrically represent "weighted" Argumentation frameworks (AF): different kinds of preference levels related to arguments, e.g. a score representing a "fuzziness", a "cost" or a probability level of each argument, can be represented by choosing different semirings. The novel idea is to provide a common computational and quantitative framework where attacks (and/or supports) have an associated weight and, consequently, also the computation of the classical Dung's semantics has an associated weight representing how much inconsistency we tolerate in the solution. The proposed semiring-based AF is then casted into a Soft Constraint Satisfaction Problem. Adding suitable sets of constraints permits to characterize the solution of the soft CSP as the desired Dung semantics. This allows for the application of the several solution techniques developed for Soft CSPs to AFs.

@conference{
	11391_1158904,
	author = {Bistarelli, Stefano and Daniele, Pirolandi and Santini, Francesco},
	title = {Solving Weighted Argumentation Farmeworks with Soft Constraints},
	year = {2010},
	publisher = {CEUR-WS.org},
	volume = {598},
	booktitle = {Proceedings of the 25th Italian Conference on Computational Logic}
}

@article{
	11391_121122,
	author = {Bistarelli, Stefano and Santini, Francesco},
	title = {Implementing and Testing a Formal Framework for Constraint-Based Routing over Scale-free Networks},
	year = {2009},
	journal = {INTERNATIONAL JOURNAL ON ADVANCES IN NETWORKS AND SERVICES},
	volume = {2},
	url = {http://www.iariajournals.org/networks_and_services/},
	pages = {13--24}
}

@conference{
	11391_121121,
	author = {Bistarelli, Stefano and Santini, Francesco},
	title = {A Nonmonotonic Soft Concurrent Constraint Language for SLA Negotiation},
	year = {2009},
	publisher = {ELSEVIER},
	journal = {ELECTRONIC NOTES IN THEORETICAL COMPUTER SCIENCE},
	volume = {236},
	booktitle = {Proceedings of the 3rd International Workshop on Views On Designing Complex Architectures (VODCA 2008)},
	abstract = {We present an extension of the Soft Concurrent Constraint language that allows the nonmonotonic evolution of the constraint store. To accomplish this, we introduce some new operations: the retract(c) reduces the current store by c, the updateX(c) transactionally relaxes all the constraints of the store that deal with the variables in the set X, and then adds a constraint c; the nask(c) tests if c is not entailed by the store. We present this framework as a possible solution to the management of resources (e.g. web services and network resource allocation) that need a given Quality of Service (QoS). The QoS requirements of all the parties should converge, through a negotiation process, on a formal agreement defined as the Service Level Agreement, which specifies the contract that must be enforced. c-semirings are the algebraic structures that we use to model QoS metrics.},
	keywords = {soft constraint logic programming; nonmonotonicity; quality of service; service level agreement},
	doi = {10.1016/j.entcs.2009.03.020},	
	pages = {147--162}
}

We present an extension of the Soft Concurrent Constraint language that allows the nonmonotonic evolution of the constraint store. To accomplish this, we introduce some new operations: the retract(c) reduces the current store by c, the updateX(c) transactionally relaxes all the constraints of the store that deal with the variables in the set X, and then adds a constraint c; the nask(c) tests if c is not entailed by the store. We present this framework as a possible solution to the management of resources (e.g. web services and network resource allocation) that need a given Quality of Service (QoS). The QoS requirements of all the parties should converge, through a negotiation process, on a formal agreement defined as the Service Level Agreement, which specifies the contract that must be enforced. c-semirings are the algebraic structures that we use to model QoS metrics.

@article{
	11391_121119,
	author = {Bistarelli, Stefano and Codognet, Philippe and Hui, H. K. C. and Lee, J. H. M.},
	title = {Solving finite domain constraint hierarchies by local consistency and tree search},
	year = {2009},
	journal = {JOURNAL OF EXPERIMENTAL & THEORETICAL ARTIFICIAL INTELLIGENCE},
	volume = {21},
	abstract = {We provide a reformulation of the constraint hierarchies (CHs) framework based on the notion of error indicators. Adapting the generalised view of local consistency in semiring-based constraint satisfaction problems, we define constraint hierarchy k-consistency (CH-k-C) and give a CH-2-C enforcement algorithm. We demonstrate how the CH-2-C algorithm can be seamlessly integrated into the ordinary branch-and-bound algorithm to make it a finite domain (FD) CH solver. Experimentation confirms the efficiency and robustness of our proposed solver prototype. Unlike other FD CH solvers, our proposed method works for both local and global comparators. In addition, our solver can support arbitrary error functions.},
	keywords = {Constraint hierarchies, Soft constraints, Local consistency},
	doi = {10.1080/09528130802667690},	
	pages = {233--257}
}

We provide a reformulation of the constraint hierarchies (CHs) framework based on the notion of error indicators. Adapting the generalised view of local consistency in semiring-based constraint satisfaction problems, we define constraint hierarchy k-consistency (CH-k-C) and give a CH-2-C enforcement algorithm. We demonstrate how the CH-2-C algorithm can be seamlessly integrated into the ordinary branch-and-bound algorithm to make it a finite domain (FD) CH solver. Experimentation confirms the efficiency and robustness of our proposed solver prototype. Unlike other FD CH solvers, our proposed method works for both local and global comparators. In addition, our solver can support arbitrary error functions.

@conference{
	11391_143646,
	author = {Bistarelli, Stefano and Santini, Francesco},
	title = {Soft Constraints for Dependable Service Oriented Architectures},
	year = {2009},
	publisher = {Springer},
	volume = {5835},
	booktitle = {DSN 2008: Workshop on Software Architectures for Dependable Systems (WADS)},
	abstract = {We propose the use of Soft Constraints as a natural way to model Service Oriented Architecture. In the framework, constraints are used to model components and connectors and constraint aggregation is used to represent their interactions. Moreover, a specific constraint projection operator is used to highlight the service interface. The quality of a service is measured and considered when performing queries to service providers. In particular, we are here interested to aspect of dependability, that is to the trustworthiness of a computing system on the service it delivers. In our framework, the dependability score is represented by the softness level of the constraint and the measure of complex (web) services is computed by combining the levels of the components. The framework takes also in account the interaction of software agents representing distributed services, by using a constraint based concurrent language able to also decide the collaboration taking care of the required dependability score.},
	doi = {10.1007/978-3-642-10248-6_4},	
	pages = {76--97}
}

We propose the use of Soft Constraints as a natural way to model Service Oriented Architecture. In the framework, constraints are used to model components and connectors and constraint aggregation is used to represent their interactions. Moreover, a specific constraint projection operator is used to highlight the service interface. The quality of a service is measured and considered when performing queries to service providers. In particular, we are here interested to aspect of dependability, that is to the trustworthiness of a computing system on the service it delivers. In our framework, the dependability score is represented by the softness level of the constraint and the measure of complex (web) services is computed by combining the levels of the components. The framework takes also in account the interaction of software agents representing distributed services, by using a constraint based concurrent language able to also decide the collaboration taking care of the required dependability score.

@conference{
	11391_143883,
	author = {Bistarelli, Stefano and Campli, Paola},
	title = {Fairness as a QoS Measure for Web Services},
	year = {2009},
	publisher = {--},
	journal = {ELECTRONIC PROCEEDINGS IN THEORETICAL COMPUTER SCIENCE},
	volume = {2},
	booktitle = {Proceedings Fourth European Young Researchers Workshop on  Service Oriented Computing},
	doi = {10.4204/EPTCS.2.9},	
	pages = {115--127}
}

@misc{
	11391_146887,
	author = {Bistarelli, Stefano and Monfroy, Eric and O'Sullivan, Barry},
	title = {Proceedings of the 2009 ACM Symposium on Applied Computing - Constraint solving and programming track},
	year = {2009},
	publisher = {ACM Press},
	abstract = {atti di convegno.}
}

atti di convegno.

@conference{
	11391_143834,
	author = {Bistarelli, Stefano and Gosti, Giorgio},
	title = {Solving CSPs with Naming Games},
	year = {2009},
	publisher = {Springer},
	volume = {5655},
	booktitle = {Revised Selected Papers Recent Advances in Constraints, CSCLP. June 18-20, 2008},
	abstract = {Revised Selected Papers
Recent Advances in Constraints, CSCLP.
June 18-20, 2008.
Rome, Italy.
Springer.
AMSTERDAM.
ISBN: 9783642032509},
	doi = {10.1007/978-3-642-03251-6_2},	
	pages = {16--32}
}

Revised Selected Papers Recent Advances in Constraints, CSCLP. June 18-20, 2008. Rome, Italy. Springer. AMSTERDAM. ISBN: 9783642032509

@conference{
	11391_143884,
	author = {Bistarelli, Stefano and Santini, Francesco},
	title = {Soft Constraints for Quality Aspects in Service Oriented                Architectures},
	year = {2009},
	publisher = {Open Publishing Association},
	journal = {ELECTRONIC PROCEEDINGS IN THEORETICAL COMPUTER SCIENCE},
	volume = {2},
	booktitle = {Proceedings Fourth European Young Researchers Workshop on  Service Oriented Computing},
	doi = {10.4204/EPTCS.2.5},	
	pages = {51--65}
}

@conference{
	11391_143645,
	author = {Bistarelli, Stefano and Santini, Francesco},
	title = {C-semiring Frameworks for Minimum Spanning Tree Problems},
	year = {2009},
	publisher = {Springer},
	volume = {5486},
	booktitle = {Recent Trends in Algebraic Development Techniques, 19th International Workshop, WADT 2008},
	abstract = {In this paper we define general algebraic frameworks for the Minimum Spanning Tree problem based on the structure of c-semirings. We propose general algorithms that can compute such trees by following different cost criteria, which must be all specific instantiation of c-semirings. Our algorithms are extensions of well-known procedures, as Prim or Kruskal, and show the expressivity of these algebraic structures. They can deal also with partially-ordered costs on the edges.},
	doi = {10.1007/978-3-642-03429-9_5},	
	pages = {56--70}
}

In this paper we define general algebraic frameworks for the Minimum Spanning Tree problem based on the structure of c-semirings. We propose general algorithms that can compute such trees by following different cost criteria, which must be all specific instantiation of c-semirings. Our algorithms are extensions of well-known procedures, as Prim or Kruskal, and show the expressivity of these algebraic structures. They can deal also with partially-ordered costs on the edges.

@conference{
	11391_143835,
	author = {Bistarelli, Stefano and Foley, SIMON N. and O'Sullivan, Barry and Santini, Francesco},
	title = {From Marriages to Coalitions: A Soft CSP Approach},
	year = {2009},
	publisher = {Springer},
	volume = {5655},
	booktitle = {Revised Selected Papers Recent Advances in Constraints, CSCLP 2008},
	abstract = {In this work we represent the Optimal Stable Marriage problem as a Soft Constraint Satisfaction Problem. In addition, we extend this problem from couples of individuals to coalitions of generic agents, in order to define new coalition-formation principles and stability conditions. In the coalition case, we suppose the preference value as a trust score, since trust can describe the belief of a node in the capabilities of another node, in its honesty and reliability. Semiring-based soft constraints represent a general and expressive framework that is able to deal with distinct concepts of optimality by only changing the related c-semiring structure, instead of using different ad-hoc algorithms. At last, we propose an implementation of the classical OSM problem using integer linear programming tools.},
	doi = {10.1007/978-3-642-03251-6_1},	
	pages = {1--15}
}

In this work we represent the Optimal Stable Marriage problem as a Soft Constraint Satisfaction Problem. In addition, we extend this problem from couples of individuals to coalitions of generic agents, in order to define new coalition-formation principles and stability conditions. In the coalition case, we suppose the preference value as a trust score, since trust can describe the belief of a node in the capabilities of another node, in its honesty and reliability. Semiring-based soft constraints represent a general and expressive framework that is able to deal with distinct concepts of optimality by only changing the related c-semiring structure, instead of using different ad-hoc algorithms. At last, we propose an implementation of the classical OSM problem using integer linear programming tools.

@conference{
	11391_1002067,
	author = {Campli, Paola and Bistarelli, Stefano},
	title = {Capturing Fair Computations on Concurrent Constraint Language},
	year = {2009},
	publisher = {Springer},
	journal = {LECTURE NOTES IN COMPUTER SCIENCE},
	volume = {5649},
	booktitle = {Logic Programming},
	doi = {10.1007/978-3-642-02846-5_63},	
	pages = {559--560}
}

@conference{
	11391_1002066,
	author = {Bottalico, Marco and Bistarelli, Stefano},
	title = {Constraint Based Languages for Biological Reactions},
	year = {2009},
	publisher = {Springer},
	journal = {LECTURE NOTES IN COMPUTER SCIENCE},
	volume = {5649},
	booktitle = {Logic Programming},
	doi = {10.1007/978-3-642-02846-5_64},	
	pages = {561--562}
}

@article{
	11391_121118,
	author = {Bella, Giampaolo and Bistarelli, Stefano and Massacci, Fabio},
	title = {Retaliation Against Protocol Attacks},
	year = {2008},
	journal = {JOURNAL OF INFORMATION ASSURANCE AND SECURITY},
	volume = {3},
	abstract = {Security protocols intend to give their parties reasonable assurance that certain security properties will protect their communication session. However, the literature confirms that the protocols may suffer subtle and hidden attacks. Flawed protocols are customarily sent back to the design process, but the costs of reengineering a deployed protocol may be prohibitive. This paper outlines the concept of retaliation: who would steal a sum of money today, should this pose significant risks of having twice as much stolen back tomorrow? When ethics is left behind, attacks are always balanced decisions: if an attack can be retaliated, the economics of security may convince the attacker to refrain from attacking, and us to live with a flawed protocol. This new perspective requires a new threat model where any party may decide to subvert the protocol for his own sake, depending on the risks of retaliation. This threat model, which for example is also suitable to studying non-repudiation protocols, seems more appropriate than the Dolev-Yao model to the present technological/social setting. It is demonstrated that machine-assisted protocol verification can and must be tailored to the new threat model.},
	pages = {313--325}
}

Security protocols intend to give their parties reasonable assurance that certain security properties will protect their communication session. However, the literature confirms that the protocols may suffer subtle and hidden attacks. Flawed protocols are customarily sent back to the design process, but the costs of reengineering a deployed protocol may be prohibitive. This paper outlines the concept of retaliation: who would steal a sum of money today, should this pose significant risks of having twice as much stolen back tomorrow? When ethics is left behind, attacks are always balanced decisions: if an attack can be retaliated, the economics of security may convince the attacker to refrain from attacking, and us to live with a flawed protocol. This new perspective requires a new threat model where any party may decide to subvert the protocol for his own sake, depending on the risks of retaliation. This threat model, which for example is also suitable to studying non-repudiation protocols, seems more appropriate than the Dolev-Yao model to the present technological/social setting. It is demonstrated that machine-assisted protocol verification can and must be tailored to the new threat model.

@conference{
	11391_121117,
	author = {Bistarelli, Stefano and Peretti, Pamela and Trubitsyna, Irina},
	title = {Analyzing security scenarios using Defence Trees and Answer Set Programming},
	year = {2008},
	publisher = {ELSEVIER},
	journal = {ELECTRONIC NOTES IN THEORETICAL COMPUTER SCIENCE},
	volume = {197},
	booktitle = {Proceedings of the 3rd International Workshop on Security and Trust Management (STM 2007)},
	abstract = {Defence trees are used to represent attack and defence strategies in security scenarios; the aim in such scenarios is to select the best set of countermeasures that are able to stop all the vulnerabilities.

In order to represent preferences among possible countermeasures of a given attack, defence trees are enriched with conditional preferences, obtaining a new structure called CP-defence tree. In this paper we transform a CP-defence tree with preferences among attacks and countermeasures in an Answer Set Optimization (ASO) program. The ASO program, representing the overall scenario, is a special composition of the programs associated to each branch of a CP-defence tree. We describe an implementation that select the best set of countermeasure able to mitigate all the vulnerabilities by computing the optimal answer set of the corresponding ASO program.},
	keywords = {Defence tree; Answer Set Programming; CR-Prolog},
	doi = {10.1016/j.entcs.2007.12.021},	
	pages = {121--129}
}

Defence trees are used to represent attack and defence strategies in security scenarios; the aim in such scenarios is to select the best set of countermeasures that are able to stop all the vulnerabilities. In order to represent preferences among possible countermeasures of a given attack, defence trees are enriched with conditional preferences, obtaining a new structure called CP-defence tree. In this paper we transform a CP-defence tree with preferences among attacks and countermeasures in an Answer Set Optimization (ASO) program. The ASO program, representing the overall scenario, is a special composition of the programs associated to each branch of a CP-defence tree. We describe an implementation that select the best set of countermeasure able to mitigate all the vulnerabilities by computing the optimal answer set of the corresponding ASO program.

@inbook{
	11391_131196,
	author = {Bistarelli, Stefano and Rossi, Francesca},
	title = {Semiring-Based Soft Constraints},
	year = {2008},
	publisher = {Springer},
	volume = {5065},
	booktitle = {Concurrency, Graphs and Models, Essays Dedicated to Ugo Montanari on the Occasion of His 65th Birthday},
	abstract = {The semiring-based formalism to model soft constraint has been introduced in 1995 by Ugo Montanari and the authors of this paper. The idea was to make constraint programming more flexible and widely applicable. We also wanted to define the extension via a general formalism, so that all its instances could inherit its properties and be easily compared. Since then, much work has been done to study, extend, and apply this formalism. This papers gives a brief summary of some of these research activities.},
	pages = {155--173}
}

The semiring-based formalism to model soft constraint has been introduced in 1995 by Ugo Montanari and the authors of this paper. The idea was to make constraint programming more flexible and widely applicable. We also wanted to define the extension via a general formalism, so that all its instances could inherit its properties and be easily compared. Since then, much work has been done to study, extend, and apply this formalism. This papers gives a brief summary of some of these research activities.

@misc{
	11391_146837,
	author = {Bistarelli, Stefano and Monfroy, Eric and O'Sullivan, Barry},
	title = {Proceedings of the 2008 ACM Symposium on Applied Computing - Constraint solving and programming track},
	year = {2008},
	publisher = {ACM Press},
	abstract = {atti di convegno.}
}

atti di convegno.

@conference{
	11391_161113,
	author = {Bistarelli, Stefano and Gabbrielli, Maurizio and Meo, Maria Chiara and Santini, Francesco},
	title = {Timed Soft Concurrent Constraint Programs},
	year = {2008},
	publisher = {Springer},
	volume = {5052},
	booktitle = {Coordination Models and Languages, 10th International Conference, COORDINATION 2008},
	abstract = {We propose a timed and soft extension of Concurrent Constraint Programming. The time extension is based on the hypothesis of bounded asynchrony: the computation takes a bounded period of time and is measured by a discrete global clock. Action prefixing is then considered as the syntactic marker which distinguishes a time instant from the next one. Supported by soft constraints instead of crisp ones, tell and ask agents are now equipped with a preference (or consistency) threshold which is used to determine their success or suspension. In the paper we provide a language to describe the agents behavior, together with its operational and denotational semantics, for which we also prove the compositionality and correctness properties. Agents negotiating Quality of Service can benefit from this new language, by coordinating among themselves and mediating their preferences.},
	doi = {10.1007/978-3-540-68265-3_4},	
	pages = {50--66}
}

We propose a timed and soft extension of Concurrent Constraint Programming. The time extension is based on the hypothesis of bounded asynchrony: the computation takes a bounded period of time and is measured by a discrete global clock. Action prefixing is then considered as the syntactic marker which distinguishes a time instant from the next one. Supported by soft constraints instead of crisp ones, tell and ask agents are now equipped with a preference (or consistency) threshold which is used to determine their success or suspension. In the paper we provide a language to describe the agents behavior, together with its operational and denotational semantics, for which we also prove the compositionality and correctness properties. Agents negotiating Quality of Service can benefit from this new language, by coordinating among themselves and mediating their preferences.

@conference{
	11391_143640,
	author = {Bistarelli, Stefano and Santini, Francesco},
	title = {SCLP for Trust Propagation in Small-World Networks},
	year = {2008},
	publisher = {Springer},
	volume = {5129},
	booktitle = {Recent Advances in Constraints, 12th Annual ERCIM International Workshop on Constraint Solving and Constraint Logic Programming, CSCLP 2007.},
	abstract = {We propose Soft Constraint Logic Programming based on semirings as a mean to easily represent and evaluate trust propagation in small-world networks. To attain this, we model the trust network adapting it to a weighted and-or graph, where the weight on a connector corresponds to the trust and confidence feedback values among the connected nodes. Semirings are the parametric and flexible structures used to appropriately represent trust metrics. Social (and not only) networks present small-world properties: most nodes can be reached from every other by a small number of hops. These features can be exploited to reduce the computational complexity of the model. In the same model we also introduce the concept of multitrust, which is aimed at computing trust by collectively involving a group of trustees at the same time.},
	doi = {10.1007/978-3-540-89812-2_3},	
	pages = {32--46}
}

We propose Soft Constraint Logic Programming based on semirings as a mean to easily represent and evaluate trust propagation in small-world networks. To attain this, we model the trust network adapting it to a weighted and-or graph, where the weight on a connector corresponds to the trust and confidence feedback values among the connected nodes. Semirings are the parametric and flexible structures used to appropriately represent trust metrics. Social (and not only) networks present small-world properties: most nodes can be reached from every other by a small number of hops. These features can be exploited to reduce the computational complexity of the model. In the same model we also introduce the concept of multitrust, which is aimed at computing trust by collectively involving a group of trustees at the same time.

@conference{
	11391_161102,
	author = {Bistarelli, Stefano and Martinelli, Fabio and Santini, Francesco},
	title = {Weighted Datalog and Levels of Trust},
	year = {2008},
	publisher = {IEEE Computer Society Press},
	booktitle = {Proceedings of the The Third International Conference on Availability, Reliability and Security, ARES 2008, March 4-7, 2008, Technical University of Catalonia, Barcelona, Spain},
	abstract = {We extend the Datalog language (we call it Datalog^W)in order to deal with weights on ground facts and to consequently compute a feedback result for the goal satisfaction. The weights are chosen from a proper c-semiring. As a second step, in order to show the usefulness of the language, we use DatalogW as the basis to give a uniform semantics to declarative RTW (Trust Management) language family, in order to represent trust levels based on c-semirings. In this way it is possible to manage a score corresponding to a preference or cost associated to the revealed credentials, instead of a plain “yes or no” authorization result. Clearly, such a solution is more informative and allows us to treat uncertainty of facts and rules application, or different preferencesfor the entity roles. Trust can be then derived by choosing the best chain. The approach is rather generic and could be applied to other trust management languages.},
	doi = {10.1109/ARES.2008.197},	
	pages = {1128--1134}
}

We extend the Datalog language (we call it Datalog^W)in order to deal with weights on ground facts and to consequently compute a feedback result for the goal satisfaction. The weights are chosen from a proper c-semiring. As a second step, in order to show the usefulness of the language, we use DatalogW as the basis to give a uniform semantics to declarative RTW (Trust Management) language family, in order to represent trust levels based on c-semirings. In this way it is possible to manage a score corresponding to a preference or cost associated to the revealed credentials, instead of a plain “yes or no” authorization result. Clearly, such a solution is more info