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Abducible Semantics and Argumentation

Osorio M., Carballido J. L., Zepeda C.

Fundamenta Informaticae

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2017

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Vol. 155, nr 3

293--319

EN

We extend further the relationship that exists between logic programming semantics and some of the semantics of extensions defined on argumentation frameworks. We define a new logic programming semantics based on the addition of abducible atoms to those normal logic programs that do not have stable models, and consider the argumentation extensions that result from it when using a well-known translation mapping between argumentation frameworks and normal programs. We call this programming semantics the stable m-ab-m logic programming semantics. This semantics defines a new type of semantics of extensions on argumentation frameworks that is not comparable to the semi-stable argumentation semantics, yet both argumentation semantics share several properties, since they both generalize the stable semantics of extensions. We also define a semantics for normal logic programs based on minimal classical two-valued models and the Gelfond-Lifschitz reduct. This semantics corresponds to the semi-stable extensions in argumentation frameworks according to the mapping mentioned before; this way we obtain a general version of a semi-stable semantics for normal logic programs. Each of these new semantics has the property of being non-empty for any normal logic program or argumentation framework, and each of them agrees with the respective stable semantics in the case where the stable semantics is a non-empty set.

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RTT+ - Time Validity Constraints in RTT Language

Felkner A., Kozakiewicz A.

Journal of Telecommunications and Information Technology

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2012

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nr 2

74-82

EN

Most of the traditional access control models, like mandatory, discretionary and role based access control make authorization decisions based on the identity, or the role of the requester, who must be known to the resource owner. Thus, they may be suitable for centralized systems but not for decentralized environments, where the requester and service provider or resource owner are often unknown to each other. To overcome the shortcomings of traditional access control models, trust management models have been presented. The topic of this paper is three different semantics (set-theoretic, operational, and logic- programming) of RTT , language from the family of role-based trust management languages (RT). RT is used for representing security policies and credentials in decentralized, distributed access control systems. A credential provides information about the privileges of users and the security policies issued by one or more trusted authorities. The set-theoretic semantics maps roles to a set of sets of entity names. Members of such a set must cooperate in order to satisfy the role. In the case of logic-programming semantics, the credentials are translated into a logic program. In the operational semantics the credentials can be established using a simple set of inference rules. It turns out to be fundamental mainly in large- scale distributed systems, where users have only partial view of their execution context. The core part of this paper is the introduction of time validity constraints to show how that can make RTT language more realistic. The new language, named RTT+ takes time validity constraints into account. The semantics for RTT+ language will also be shown. Inference system will be introduced not just for specific moment but also for time intervals. It will evaluate maximal time validity, when it is possible to derive the credential from the set of available credentials. The soundness and completeness of the inference systems with the time validity constraints with respect to the set-theoretic semantics of RTT+ will be proven.

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A Schema for Generating Relevant Logic Programming Semantics and its Applications in Argumentation Theory

Nieves J.C., Osorio M., Zepeda C.

Fundamenta Informaticae

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2011

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Vol. 106, nr 2-4

295-311

EN

In the literature, there are several approaches which try to perform common sense reasoning. Among them, the approaches which have probably received the most attention the last two decades are the approaches based on logic programming semantics with negation as failure and argumentation theory. Even though both approaches have their own features, it seems that they share some common behaviours which can be studied by considering the close relationship between logic programming semantics and extension-based argumentation semantics. In this paper, we will present a general recursive schema for defining new logic programming semantics. This schema takes as input any basic logic programming semantics, such as the stable model semantics, and gives as output a new logic programming semantics which satisfies some desired properties such as relevance and the existence of the intended models for every normal program. We will see that these new logic programming semantics can define candidate extension-based argumentation semantics. These new argumentation semantics will overcome some of the weakness of the extension-based argumentation semantics based on admissible sets. In fact, we will see that some of these new argumentation semantics have similar behaviour to the extension-based argumentation semantics built in terms of strongly connected components.