Papers by Guido Governatori
Advances in Modal Logic, 2004
European Conference on Artificial Intelligence, 2016
In computational models of argumentation, argument justification has attracted more attention tha... more In computational models of argumentation, argument justification has attracted more attention than statement justification, and significant sensitivity losses are identifiable when dealing with the justification of statements by otherwise appealing formalisms. This paper reappraises statement justification as a formalism-independent component in argument-based reasoning. We introduce a novel general model of argument-based reasoning based on multiple stages of labellings, the last one being devoted to statement justification, identify two alternative paths from argument acceptance to statement justification, and compare their expressiveness. We then show that this model encompasses several prominent literature proposals as special cases, thereby enabling a systematic comparison of existing approaches to statement justification, evidencing their merits and limits. Finally we illustrate our model by specifying a generic ignorance-aware statement justification and showing how it can be seamlessly integrated into different formalisms.
Adaptive Agents and Multi-Agents Systems, May 9, 2016
Probabilistic argumentation combines the quantitative uncertainty accounted by probability theory... more Probabilistic argumentation combines the quantitative uncertainty accounted by probability theory with the qualitative uncertainty captured by argumentation. In this paper, we investigate the problem of learning the structure of an argumentative graph to account for (a distribution of) labellings of a set of arguments. We consider a general abstract framework, where the structure of arguments is left unspecified, and we focus on the grounded semantics. We present, with experimental insights, an anytime algorithm evaluating 'on the fly' hypothetical attacks from the examination of an input stream of labellings.
arXiv (Cornell University), Nov 15, 2005
Defeasible reasoning is a simple but efficient approach to nonmonotonic reasoning that has recent... more Defeasible reasoning is a simple but efficient approach to nonmonotonic reasoning that has recently attracted considerable interest and that has found various applications. Defeasible logic and its variants are an important family of defeasible reasoning methods. So far no relationship has been established between defeasible logic and mainstream nonmonotonic reasoning approaches. In this paper we establish close links to known semantics of logic programs. In particular, we give a translation of a defeasible theory D into a meta-program P (D). We show that under a condition of decisiveness, the defeasible consequences of D correspond exactly to the sceptical conclusions of P (D) under the stable model semantics. Without decisiveness, the result holds only in one direction (all defeasible consequences of D are included in all stable models of P (D)). If we wish a complete embedding for the general case, we need to use the Kunen semantics of P (D), instead.
Indian International Conference on Artificial Intelligence, 2011
Adaptive Agents and Multi-Agents Systems, Jun 4, 2012
In this paper we study isolation as a form of punishment. Although an isolated violator is punish... more In this paper we study isolation as a form of punishment. Although an isolated violator is punished as it can not benefit from the interactions with other agents, compliant agents may also suffer from not engaging with the violators. In this paper we analyze such problems. Certain modifications of multi agent systems are needed to solve this problem. These modifications are aimed to make the violator redundant so that it can be ignored and hence isolated. Deciding on these modifications is NP-complete and approximation algorithms exist.
We shall argue that burdens of proof are relevant also to monological reasoning, i.e., for derivi... more We shall argue that burdens of proof are relevant also to monological reasoning, i.e., for deriving the conclusions of a knowledge-base allowing for conflicting arguments. Reasoning with burdens of proof can provide a useful extension of current argument-based non-monotonic logics, at least a different perspective on them. Firstly we shall provide an objective characterisation of burdens of proof, assuming that burdens concerns rule antecedents (literals in the body of rules), rather than agents. Secondly, we shall analyse the conditions for a burden to be satisfied, by considering credulous or skeptical derivability of the concerned antecedent or of its complement. Finally, we shall develop a method for developing inferences out of a knowledge base merging rules and proof burdens in the framework of defeasible logic.
We study the complexity of the Strategic Argumentation Problem for 2-player dialogue games where ... more We study the complexity of the Strategic Argumentation Problem for 2-player dialogue games where a player should decide what move (set of rules) to play at each turn in order to prove (disprove) a given thesis. We show that this is an NP-complete problem.
Artificial Intelligence and Law, Feb 23, 2018
Decision-makers in governments, enterprises, businesses and agencies or individuals, typically, m... more Decision-makers in governments, enterprises, businesses and agencies or individuals, typically, make decisions according to various regulations, guidelines and policies based on existing records stored in various databases, in particular, relational databases. To assist decision-makers, an expert system, encompasses interactive computer-based systems or subsystems to support the decision-making process. Typically, most expert systems are built on top of transaction systems, databases, and data models and restricted in decision-making to the analysis, processing and presenting data and information, and they do not provide support for the normative layer. This paper will provide a solution to one specific problem that arises from this situation, namely the lack of tool/mechanism to demonstrate how an expert system is well-suited for supporting decision-making activities drawn from existing records and relevant legal requirements aligned existing records stored in various databases.We present a Rule-based (pre and post) reporting systems (RuleRS) architecture, which is intended to integrate databases, in particular, relational databases, with a logic-based reasoner and rule engine to assist in decision-making or create reports according to legal norms. We argue that the resulting RuleRS provides an efficient and flexible solution to the problem at hand using defeasible inference. To this end, we have also conducted empirical evaluations of RuleRS performance.
Principles of Knowledge Representation and Reasoning, May 9, 2010
If compliance with a norm does not achieve its purpose, then its applicability must dynamically b... more If compliance with a norm does not achieve its purpose, then its applicability must dynamically be restricted or expanded. Legal interpretation is a mechanism from law allowing norms to be adapted to unforeseen situations. We model this mechanism for norms regulating computer systems by representing the purpose of norms by social goals and by revising the constitutive rules defining the applicability of norms. We illustrate the interpretation mechanism by examples.
PubMed, 2010
Temporal information plays a crucial role in medicine, so that in Medical Informatics there is an... more Temporal information plays a crucial role in medicine, so that in Medical Informatics there is an increasing awareness that suitable database approaches are needed to store and support it. Specifically, a great amount of clinical data (e.g., therapeutic data) are periodically repeated. Although an explicit treatment is possible in most cases, it causes severe storage and disk I/O problems. In this paper, we propose an innovative approach to cope with periodic medical data in an implicit way. We propose a new data model, representing periodic data in a compact (implicit) way, which is a consistent extension of TSQL2 consensus approach. Then, we identify some important types of temporal queries, and present query answering algorithms to answer them. We also sketch a temporal relational algebra for our approach. Finally, we show experimentally that our approach outperforms current explicit approaches.
Artificial Intelligence and Law, Jan 10, 2019
This paper presents a belief revision operator that considers time intervals for modelling norm c... more This paper presents a belief revision operator that considers time intervals for modelling norm change in the law. This approach relates techniques from belief revision formalisms and time intervals with temporalised rules for legal systems. Our goal is to formalise a temporalised belief base and corresponding timed derivation, together with a proper revision operator. This operator may remove rules when needed or adapt intervals of time when contradictory norms are added in the system. For the operator, both constructive definition and an axiomatic characterisation by representation theorems are given.
Artificial Intelligence and Law, Sep 20, 2017
The effectiveness of a compliance management framework (CMF) can be guaranteed only if the framew... more The effectiveness of a compliance management framework (CMF) can be guaranteed only if the framework is based on sound conceptual and formal foundations. In particular, the formal language used in the CMF is able to expressively represent the specifications of normative requirements (hereafter, norms) that impose constraints on various activities of a business process. However, if the language used lacks expressiveness and the modelling constructs proposed in the CMF are not able to properly represent different types of norms, it can significantly impede the reliability of the compliance results produced by the CMF. This paper investigates whether existing CMFs are able to provide reasoning and modeling support for various types of normative requirements by evaluating the conceptual foundations of the modeling constructs that existing CMFs use to represent a specific type of norm. The evaluation results portray somewhat a bleak picture of the state-of-the-affairs when it comes to represent norms as none of the existing CMFs is able to provide a comprehensive reasoning and modeling support. Also, it points to the shortcomings of the CMFs and emphasises exigent need of new modeling languages with sound theoretical and formal foundations for representing legal norms.
International Conference on Legal Knowledge and Information Systems, 2012
We propose a framework for reconstructing the arguments supporting the restrictive interpretation... more We propose a framework for reconstructing the arguments supporting the restrictive interpretations of legal provisions. e idea is that the interpretation of legal concepts may require to change the counts-as rules de ning them. Some connections with revision theory techniques are considered.
In stream authentication protocols used for largescale data dissemination in autonomuous systems,... more In stream authentication protocols used for largescale data dissemination in autonomuous systems, authentication is based on the timing of the publication of keys, and depends on trust of the receiver in the sender and belief on whether an intruder can have prior knowledge of a key before it is published by a protocol. Many existing logics and approaches have successfully been applied to specify other types of authentication protocols, but most of them are not appropriate for analysing stream authentication protocols. We therefore consider a fibred modal logic that combines a belief logic with a linear-time temporal logic which can be used to analyse time-varying aspects of certain problems. With this logical system one is able to build theories of trust for analysing stream authentication protocols, which can deal with not only agent beliefs but also the timing properties of an autonomous agent-based system.
Lecture Notes in Computer Science, 2010
This paper proposes a logical framework to capture the norm change power and the limitations of t... more This paper proposes a logical framework to capture the norm change power and the limitations of the judicial system in revising the set of constitutive rules defining the concepts on which the applicability of norms is based. In particular, we reconstruct the legal arguments leading to an extensive or restrictive interpretation of norms.
Springer eBooks, 2000
Defeasible logic is a simple but efficient rule-based non-monotonic logic. It has powerful implem... more Defeasible logic is a simple but efficient rule-based non-monotonic logic. It has powerful implementations and shows promise to be applied in the areas of legal reasoning and the modelling of business rules. So far defeasible logic has been defined only proof-theoretically. Argumentation-based semantics have become popular in the area of logic programming. In this paper we give an argumentation-based semantics for defeasible logic. Recently it has been shown that a family of approaches can be built around defeasible logic, in which different intuitions can be followed. In this paper we present an argumentation-based semantics for an ambiguity propagating logic, too. Further defeasible logics can be characterised in a similar way.
Lecture Notes in Computer Science, 2011
... BDI-logics [13,14,18] are normal1 multi-modal logics for modelling belief, desire and intenti... more ... BDI-logics [13,14,18] are normal1 multi-modal logics for modelling belief, desire and intention with three families of modal operators BELi,DESi,INTi,i ∈ Agents. ... ω |= 2iϕ iff { ω ∈ M and M ∈ Ki and ∀ω (ωRω → ω |= ϕ),or ω ∈ M, and M ∈ Ki and ∀F ∈ F,Fi(ω) |= 2iϕ. ...
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Papers by Guido Governatori