On the dynamics of default reasoning

Antoniou, Grigoris

doi:10.1002/int.10065

Cited by 11 publications

(7 citation statements)

References 15 publications

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“…The presence of elements like "warrant" and "backing" leads to a multi-layered understanding of an argument. 4 None of the mentioned structured argumentation frameworks gives a formalization of the added components of arguments such as warrants and backings. In contrast, our logic represents three layers of arguments which are codified in reason terms t justifying formulas F that are not necessarily explicitly represented at every stage of manipulating the formula t : F in the semantics.…”

Section: Introductionmentioning

confidence: 99%

A logic of defeasible argumentation: Constructing arguments in justification logic

Pandzic

2022

AAC

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In the 1980s, Pollock’s work on default reasons started the quest in the AI community for a formal system of defeasible argumentation. The main goal of this paper is to provide a logic of structured defeasible arguments using the language of justification logic. In this logic, we introduce defeasible justification assertions of the type t : F that read as “t is a defeasible reason that justifies F”. Such formulas are then interpreted as arguments and their acceptance semantics is given in analogy to Dung’s abstract argumentation framework semantics. We show that a large subclass of Dung’s frameworks that we call “warranted” frameworks is a special case of our logic in the sense that (1) Dung’s frameworks can be obtained from justification logic-based theories by focusing on a single aspect of attacks among justification logic arguments and (2) Dung’s warranted frameworks always have multiple justification logic instantiations called “realizations”. We first define a new justification logic that relies on operational semantics for default logic. One of the key features that is absent in standard justification logics is the possibility to weigh different epistemic reasons or pieces of evidence that might conflict with one another. To amend this, we develop a semantics for “defeaters”: conflicting reasons forming a basis to doubt the original conclusion or to believe an opposite statement. This enables us to formalize non-monotonic justifications that prompt extension revision already for normal default theories. Then we present our logic as a system for abstract argumentation with structured arguments. The format of conflicting reasons overlaps with the idea of attacks between arguments to the extent that it is possible to define all the standard notions of argumentation framework extensions. Using the definitions of extensions, we establish formal correspondence between Dung’s original argumentation semantics and our operational semantics for default theories. One of the results shows that the notorious attack cycles from abstract argumentation cannot always be realized as justification logic default theories.

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Section: Introductionmentioning

confidence: 99%

A logic of defeasible argumentation: Constructing arguments in justification logic

Pandzic

2022

AAC

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“…As mentioned in the introduction to this chapter, our approach to structured argumentation dynamics builds on similar ideas as Antoniou's (2002) approach to the dynamics of standard default theories. Antoniou's approach significantly differs from ours in the way he treats those changes that add or remove a formula at the level of some, but not necessarily all extensions.…”

Section: Discussionmentioning

confidence: 99%

“…Unlike our conservative expansion and conservative contraction, none of Antoniou's operations leaves the inclusion status of a formula undecided. For instance, to secure that a formula is not contained in at least one extension, Antoniou (2002Antoniou ( , p. 1149) adds a new extension where introducing the formula is blocked by adding either a new atom or its negation to any default, dependent on whether they are allowed to be in a same extension or not.…”

Section: Discussionmentioning

confidence: 99%

“…The operations we introduce combine Hansson's (1999a) base revision operations with a specific kind of standard Reiter default rules. Our approach to defining the dynamic operators for default theory revision has most in common with Antoniou's (2002) approach, which deals with the dynamics of Reiter's default theories. We show by the end of the chapter that undermining attacks on premises correspond to those dynamic operations that involve either contraction or a variant of non-prioritized contraction defined in Section 4.4.…”

Section: Dynamics In Formal Argumentationmentioning

confidence: 99%

“…Furthermore, it leaves open the possibility that F occurs in all extensions of the resulting default theory. 5 Antoniou (2002Antoniou ( , p. 1149) takes a different approach in defining a more conservative contraction operation for Reiter's default theories. His idea is to secure that there is at least one extension added that does not contain the formula removed from the set of premises.…”

Section: W −mentioning

confidence: 99%

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