ILLC-LIRa

illc-lira@list.uva.nl

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582 discussions

Next Friday: Joint LIRa-DIP Session with Alessandro Giordani
by LIRa Seminar 29 Jan '17

29 Jan '17

Dear all, next Friday we will have a joint LIRa-DIP Session! Speaker: Alessandro Giordani (Catholic University of Milan) Date and Time: Friday, February 3rd 2017, 15:30-17:00 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: An Evidence-based logic of Acceptance and Rejection. Abstract: In this paper, I am going to present logics of acceptance and rejection based on the idea that these epistemic states are frame-dependent, where a frame for an epistemic state is assumed to consist of a triple (Σ, I, S), where (i) Σ is a set of subject matters, (ii) I is a set of sources of justification, and (iii) S is a set of reference epistemic standards. The central intuition underlying such an approach is that states of acceptance and rejection are connected to epistemic justifications, where a justification is intended as a subjective ground for assuming a proposition p as a solution to a specific problem relative to subject matter σ ∈ Σ, a solution that derives from a source i ∈ I and satisfies a standard s ∈ S. In modeling this kind of states, I will extend the usual systems of epistemic logic in two directions: (i) by introducing a partition of the epistemic space into cells, corresponding to different conceptual frames; (ii) by making explicit the reference to justifiers, corresponding to elements of evidence for asserting propositions. The first step allows us to introduce a local approach to the epistemic space, thus generalizing the standard global approach. The second step allows us to generalize the constructive approach according to which assertibility has to be intended as having a procedure to obtain a proof of a proposition. As we will see, the resulting system is extremely powerful from an analytical point of view. In particular, within the system, it is possible both to provide an intuitive interpretation of the phenomena of para-completeness and para-consistency connected to rejection and to assume an intermediate standpoint on the problem as to whether rejection is to be intended as having a proof of the negation of a proposition or rather as not having a proof of the proposition. Hope to see you there! The LIRa team

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Workshop, Defence and Colloquium, but no LIRa this week.
by LIRa Seminar 22 Jan '17

22 Jan '17

Dear all, please note that there will be no LIRa session on the next Friday. However, you are all invited to the following events. Tuesday 24th, 13:00 *Workshop on Rationality, Logic, and Decisions* Place: ILLC Seminar room F1.15, Science Park 107, Amsterdam Wednesday 25th, 11:00 *PhD Defence of Paolo Galeazzi* Place: Oude Lutherse kerk, Singel 411, Amsterdam For more information, please see http://playwithoutregret.wordpress.com Friday 27th, 16:00 *ILLC New Year\'s Colloquium 2017* Place: ILLC Common room F1.21, Science Park 107, Amsterdam For more information, please see http://www.illc.uva.nl/ILLCColloquium/ILLC-New-Years-Colloquium-2017/ Hope to see you there! The LIRa team

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Tomorrow: LIRa session with Yanjing Wang
by LIRa Seminar 19 Jan '17

19 Jan '17

Dear all, tomorrow we will have our next LIRa session. Speaker: Yanjing Wang (Peking University) Date and Time: Friday, January 20th 2017, 15:30-17:00 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: A logic of knowing why. Abstract: When we say \"I know why he was late\", we know not only the fact that he was late, but also an explanation of this fact. We propose a logical framework of \"knowing why\" inspired by the existing formal studies on why-questions, scientific explanation, and justification logic. We introduce the Ky_i operator into the language of epistemic logic to express \"agent i knows why phi\'\' and propose a Kripke-style semantics of such expressions in terms of knowing an explanation of phi. We obtain two sound and complete axiomatizations w.r.t. two different model classes depending on different assumptions about introspection. (Joint work with Chao Xu and Thomas Studer.) Hope to see you there! The LIRa team

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Next Friday: LIRa session with Yanjing Wang
by LIRa Seminar 14 Jan '17

14 Jan '17

Dear all, on Friday we will have our next LIRa session. Speaker: Yanjing Wang (Peking University) Date and Time: Friday, January 20th 2017, 15:30-17:00 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: A logic of knowing why. Abstract: When we say \"I know why he was late\", we know not only the fact that he was late, but also an explanation of this fact. We propose a logical framework of \"knowing why\" inspired by the existing formal studies on why-questions, scientific explanation, and justification logic. We introduce the Ky_i operator into the language of epistemic logic to express \"agent i knows why phi\'\' and propose a Kripke-style semantics of such expressions in terms of knowing an explanation of phi. We obtain two sound and complete axiomatizations w.r.t. two different model classes depending on different assumptions about introspection. (Joint work with Chao Xu and Thomas Studer.) Hope to see you there! The LIRa team

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Tomorrow: LIRa session with Guillaume Aucher
by LIRa Seminar 12 Jan '17

12 Jan '17

Dear all, tomorrow we will have our next LIRa session. Speaker: Guillaume Aucher Date and Time: Friday, January 13th 2017, 16:00-17:30 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: Dynamic Epistemic Logic in Update Logic. Abstract: We generalize the language of substructural logics interpreted over the ternary relational semantics and we introduce a logic called update logic. This is motivated by our intention to capture within the logical framework of substructural logics various logic-based formalisms dealing with common sense reasoning and logical dynamics. This initiative is based on the key observation that an update can be represented abstractly by the ternary relation of the substructural framework. We introduce three triples of connectives which are interconnected by means of cyclic permutations. The usual fusion, implication and co-implication connectives of the Lambek calculus form one of these triples. We define a proper display calculus for our language which generalizes the display calculus for modal logic and a sequent calculus which generalizes the Lambek calculus. Using correspondence results from substructural logics, we also obtain sound and complete display calculi for a wide variety of classical and substructural logics. In particular, we show that Dynamic Epistemic Logic (DEL) is a substructural logic and that it is an extension of update logic. We identify axioms and inference rules that completely characterize the DEL product update and we provide a sequent calculus for DEL. Finally, we show that some substructural connectives of update logic can be interpreted as operators dealing with epistemic planning. Hope to see you there! The LIRa team

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This Friday: LIRa session with Guillaume Aucher
by LIRa Seminar 09 Jan '17

09 Jan '17

Dear all, this Friday we will have our next LIRa session. Speaker: Guillaume Aucher Date and Time: Friday, January 13th 2017, 16:00-17:30 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: Dynamic Epistemic Logic in Update Logic. Abstract: We generalize the language of substructural logics interpreted over the ternary relational semantics and we introduce a logic called update logic. This is motivated by our intention to capture within the logical framework of substructural logics various logic-based formalisms dealing with common sense reasoning and logical dynamics. This initiative is based on the key observation that an update can be represented abstractly by the ternary relation of the substructural framework. We introduce three triples of connectives which are interconnected by means of cyclic permutations. The usual fusion, implication and co-implication connectives of the Lambek calculus form one of these triples. We define a proper display calculus for our language which generalizes the display calculus for modal logic and a sequent calculus which generalizes the Lambek calculus. Using correspondence results from substructural logics, we also obtain sound and complete display calculi for a wide variety of classical and substructural logics. In particular, we show that Dynamic Epistemic Logic (DEL) is a substructural logic and that it is an extension of update logic. We identify axioms and inference rules that completely characterize the DEL product update and we provide a sequent calculus for DEL. Finally, we show that some substructural connectives of update logic can be interpreted as operators dealing with epistemic planning. Hope to see you there! The LIRa team

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Tomorrow: LIRa session with Alexandru Baltag
by LIRa Seminar 15 Dec '16

15 Dec '16

Dear all, tomorrow we will have our next LIRa session. Speaker: Alexandru Baltag (ILLC, Amsterdam) Date and Time: Friday, December 16th 2016, 15:30-17:00 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: Knowing the Answer. Abstract: What does it mean to \"know the answer\" to a question? What is the relationship between this form of knowledge and the usual propositional \"knowledge that\" operator? Can we know the answer without knowing the question? Can we know the answer without knowing that it is the answer to this question? I investigate logics(s) for knowing/learning answers to questions, and argue that all knowledge can in fact be reduced to this kind: at a first approximation, to know is know how to answer a question. Moreover, if questions (and answers) are properly construed, then knowledge, from an abstract point of view, is just a correlation between two questions (where the answer to the first carries information about the answer to the second). By reflection, agents can themselves come to know such correlations. In this sense, to know is to know how to use questions to answer other questions. Hope to see you there! The LIRa team

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This Friday: LIRa session with Alexandru Baltag
by LIRa Seminar 13 Dec '16

13 Dec '16

Dear all, this Friday we will have our next LIRa session. Speaker: Alexandru Baltag (ILLC, Amsterdam) Date and Time: Friday, December 16th 2016, 15:30-17:00 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: Knowing the Answer. Abstract: What does it mean to \"know the answer\" to a question? What is the relationship between this form of knowledge and the usual propositional \"knowledge that\" operator? Can we know the answer without knowing the question? Can we know the answer without knowing that it is the answer to this question? I investigate logics(s) for knowing/learning answers to questions, and argue that all knowledge can in fact be reduced to this kind: at a first approximation, to know is know how to answer a question. Moreover, if questions (and answers) are properly construed, then knowledge, from an abstract point of view, is just a correlation between two questions (where the answer to the first carries information about the answer to the second). By reflection, agents can themselves come to know such correlations. In this sense, to know is to know how to use questions to answer other questions. Hope to see you there! The LIRa team

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Tomorrow: LIRa session with Johan van Benthem
by LIRa Seminar 01 Dec '16

01 Dec '16

Dear all, tomorrow we will have our next LIRa session. Speaker: Johan van Benthem (ILLC & Stanford) Date and Time: Friday, December 2nd 2016, 15:00-16:10 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: Decidable Versions of First-Order Predicate Logic. Abstract: There are two roads to decidability in first-order logic: one restricts attention to language fragments, or one generalizes the usual semantics. I will discuss a recent semantics by Aldo Antonelli, which gives a decidable version of predicate logic with an effective translation into the Guarded Fragment. I compare this with existing decidable semantics via general assignment models, with logics of generalized quantifiers, and with the move from relational semantics to neighborhood semantics. Open problems are flagged throughout. Hope to see you there! The LIRa team

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This Friday: LIRa session with Johan van Benthem
by LIRa Seminar 28 Nov '16

28 Nov '16

Dear all, this Friday we will have our next LIRa session. Speaker: Johan van Benthem (ILLC & Stanford) Date and Time: Friday, December 2nd 2016, 15:00-16:10 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: Decidable Versions of First-Order Predicate Logic. Abstract: There are two roads to decidability in first-order logic: one restricts attention to language fragments, or one generalizes the usual semantics. I will discuss a recent semantics by Aldo Antonelli, which gives a decidable version of predicate logic with an effective translation into the Guarded Fragment. I compare this with existing decidable semantics via general assignment models, with logics of generalized quantifiers, and with the move from relational semantics to neighborhood semantics. Open problems are flagged throughout. Hope to see you there! The LIRa team

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