ILLC-LIRa May 2019

illc-lira@list.uva.nl

2 participants
10 discussions

Special LIRa Session
by LIRa Seminar 24 May '19

24 May '19

Dear all, Below you can find the details for the talks of our special LIRa session on Monday: Date and Time: Monday, May 27th 2019, 12:00-14:00 Venue: ILLC Seminar Room F1.15, Science Park 107. Speaker #1: Adam Bjorndahl (Carnegie Mellon University) Title: Measurement and Action. Abstract. In previous work (in fact, work that was first presented in the LIRa seminar!), I introduced a topological generalization of Propositional Dynamic Logic in which program executions (or, more generally, actions) are represented as fundamentally deterministic, with nondeterminism emerging as an epistemic relationship between the agent and the system. In this talk, I will review how Dynamic Topological Logic can be used to represent these notions, with actions captured by functions and possible measurements by the topology. I will then motivate a generalization of this paradigm in which the distinction between action and measurement (i.e, between functions and opens) is erased, and sketch some preliminary definitions and results in this direction. Speaker #2: Emiliano Lorini (CNRS, IRIT, Toulouse) Title: Rethinking Epistemic Logic with Belief Bases. Abstract. We introduce a semantics for a family of logics of explicit and implicit belief based on the concept of multi-agent belief base. Differently from standard semantics for epistemic logic in which the notions of possible world and doxastic/epistemic alternative are primitive, in our semantics they are non-primitive but are defined from the concept of belief base. We provide complete axiomatizations and prove decidability for our logics via finite model arguments. Furthermore, we provide polynomial embeddings of our logics into Fagin & Halpern’s logic of general awareness and establish complexity results via the embeddings. We present a number of dynamic extensions of the static framework by informative actions of both public and private type, including public announcement, belief base expansion and forgetting. Finally, we show how our belief base semantics for epistemic logic can be used to build the universal epistemic model, i.e., the epistemic model containing all possible belief hierarchies of the agents in the system. Hope to see you there! The LIRa team

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LIRa Session: Bart Verheij
by LIRa Seminar 22 May '19

22 May '19

Dear all, Tomorrow we will have our next LIRa session. You can find the details below. Also, don\'t forget about our extra session on Monday the 27th. More details will follow soon. Speaker: Bart Verheij (University of Groningen) Date and Time: Thursday, May 23rd 2019, 16:30-18:00 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: Artificial Intelligence and the Logic of Argumentation. Abstract. Argumentation has become an active field of study in Artificial Intelligence (AI). In this talk I will explain how the study of argumentation in AI has developed over the years and will argue that for good AI we need to build machines that can participate in a constructive critical discussion. By building such argumentation systems we can hope to finally bridge the long-standing gap between knowledge-based and data-driven AI. Recent work on the formalization of reasoning with evidence, rules and cases in terms of so-called case models has inspired this perspective. Hope to see you there! The LIRa team

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Special LIRa Session on Monday (27th of May)
by LIRa Seminar 20 May '19

20 May '19

Dear all, Apart from our regular LIRa session, which will take place this Thursday, there will also be a special LIRa session on Monday the 27th (12.00-14.00). The speakers will be Adam Bjorndahl (Carnegie Mellon University) and Emiliano Lorini (CNRS, IRIT, Toulouse). More details will follow soon! Hope to see you there! The LIRa team

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LIRa Session: Bart Verheij
by LIRa Seminar 17 May '19

17 May '19

Dear all, The next LIRa session will take place on Thursday, May 23rd. Please, find the details below: Speaker: Bart Verheij (University of Groningen) Date and Time: Thursday, May 23rd 2019, 16:30-18:00 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: Artificial Intelligence and the Logic of Argumentation. Abstract. Argumentation has become an active field of study in Artificial Intelligence (AI). In this talk I will explain how the study of argumentation in AI has developed over the years and will argue that for good AI we need to build machines that can participate in a constructive critical discussion. By building such argumentation systems we can hope to finally bridge the long-standing gap between knowledge-based and data-driven AI. Recent work on the formalization of reasoning with evidence, rules and cases in terms of so-called case models has inspired this perspective. Hope to see you there! The LIRa team

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LIRa Session: Thomas Schindler
by LIRa Seminar 16 May '19

16 May '19

Dear all, The next LIRa session by Thomas Schindler is later today. Please, find the details below: Speaker: Thomas Schindler (ILLC) Date and Time: Thursday, May 16th 2019, 16:30-18:00 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: Unrestricted quantification and universal classes. Abstract. According to the naive comprehension schema, an object belongs to the class of Fs iff that object is an F. Here, by class I simply understand the extension of some predicate. Due to Russell’s paradox, the naive comprehension schema is inconsistent. The orthodox solution to the class-theoretic paradoxes is found in the theory of types. However, this theory comes with severe expressive limitations, e.g. there can be no universal class (i.e. a class containing all objects). Based on some ideas of Gödel, I present a type-free theory of classes according to which there is a universal class containing all objects, including itself. I have published the basic ideas of my theory in my paper “Classes, why and how” (Phil Studies 2019). In this talk, I will survey the main ideas of this paper and also present some more recent, unpublished work on this topic. Hope to see you there! The LIRa team

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PhD Defense: Jort Bergfeld
by LIRa Seminar 14 May '19

14 May '19

Dear all, We would like to bring the following PhD defense to your attention, as it might be of interest to you: On Thursday the 16th of May Jort Bergfeld (ILLC) will defend his PhD thesis Quantum logics for expressing and proving the correctness of quantum programs The ceremony will take place at the Agnietenkapel (Oudezijds Voorburgwal 229 - 231) at 10:00. For more information, please contact Jort Bergfeld at jort.bergfeld(a)gmail.com. The LIRa team

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LIRa Session: Thomas Schindler
by LIRa Seminar 13 May '19

13 May '19

Dear all, The next LIRa session will take place on Thursday, May 16th. Please, find the details below: Speaker: Thomas Schindler (ILLC) Date and Time: Thursday, May 16th 2019, 16:30-18:00 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: Unrestricted quantification and universal classes. Abstract. According to the naive comprehension schema, an object belongs to the class of Fs iff that object is an F. Here, by class I simply understand the extension of some predicate. Due to Russell’s paradox, the naive comprehension schema is inconsistent. The orthodox solution to the class-theoretic paradoxes is found in the theory of types. However, this theory comes with severe expressive limitations, e.g. there can be no universal class (i.e. a class containing all objects). Based on some ideas of Gödel, I present a type-free theory of classes according to which there is a universal class containing all objects, including itself. I have published the basic ideas of my theory in my paper “Classes, why and how” (Phil Studies 2019). In this talk, I will survey the main ideas of this paper and also present some more recent, unpublished work on this topic. Hope to see you there! The LIRa team

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LIRa Session: Fan Yang
by LIRa Seminar 08 May '19

08 May '19

Dear all, Tomorrow we will have our next LIRa session. Please, find the details below: Speaker: Fan Yang (University of Helsinki) Date and Time: Thursday, May 9th 2019, 16:30-18:00 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: Logics for first-order team properties. Abstract. Team semantics is a semantical framework originally introduced by Hodges [1997] for the study of various dependence and independence concepts, and later systematically developed by Väänänen [2007] with the introduction of dependence logic (D). Other prominent logics based on team semantics include independence logic (Ind) [Grädel, Väänänen 2013], inclusion logic [Galliani 2012], etc. In team semantics formulas are evaluated in a model over sets of assignments (called teams) rather than single assignments as in the usual first-order logic. Teams are essentially relations, and thus open formulas define team properties. In general, knowing the expressive power of a logic for sentences (with no free variables) does not automatically give a characterization for the expressive power of open formulas of the same logic. Such a peculiar phenomenon has sparked several studies on the expressive power of logics based on team semantics. In particular, while D and Ind are both equivalent to existential second-order logic (ESO) on the level of sentences, it turns out that open formulas of Ind characterize all ESO team properties [Galliani 2012], whereas the former characterize only downward closed ESO team properties [Kontinen, Väänänen 2009]. In this talk, we introduce a logic, denoted by FOT, whose expressive power coincides with first-order logic both on the level of sentences and on the level of open formulas (in the sense that open formulas of FOT characterize exactly first-order definable team properties). We also show, as an application of Lyndon’s Interpolation Theorem, that a natural fragment of FOT captures downward closed first-order definable team properties. In the second part of the talk, we define a system of natural deduction for FOT, and show that it is sound and complete. We also discuss some applications of our logic. In particular, we demonstrate that Arrow’s Theorem in social choice can be formalized in FOT, and Armstrong’s axioms for functional dependencies in database theory can be derived in our system of FOT. (This talk is based on joint work with Juha Kontinen.) Hope to see you there! The LIRa team

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LIRa Session: Fan Yang
by LIRa Seminar 03 May '19

03 May '19

Dear all, The next LIRa session will take place on Thursday, May 9th. Please, find the details below: Speaker: Fan Yang (University of Helsinki) Date and Time: Thursday, May 9th 2019, 16:30-18:00 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: Logics for first-order team properties. Abstract. Team semantics is a semantical framework originally introduced by Hodges [1997] for the study of various dependence and independence concepts, and later systematically developed by Väänänen [2007] with the introduction of dependence logic (D). Other prominent logics based on team semantics include independence logic (Ind) [Grädel, Väänänen 2013], inclusion logic [Galliani 2012], etc. In team semantics formulas are evaluated in a model over sets of assignments (called teams) rather than single assignments as in the usual first-order logic. Teams are essentially relations, and thus open formulas define team properties. In general, knowing the expressive power of a logic for sentences (with no free variables) does not automatically give a characterization for the expressive power of open formulas of the same logic. Such a peculiar phenomenon has sparked several studies on the expressive power of logics based on team semantics. In particular, while D and Ind are both equivalent to existential second-order logic (ESO) on the level of sentences, it turns out that open formulas of Ind characterize all ESO team properties [Galliani 2012], whereas the former characterize only downward closed ESO team properties [Kontinen, Väänänen 2009]. In this talk, we introduce a logic, denoted by FOT, whose expressive power coincides with first-order logic both on the level of sentences and on the level of open formulas (in the sense that open formulas of FOT characterize exactly first-order definable team properties). We also show, as an application of Lyndon’s Interpolation Theorem, that a natural fragment of FOT captures downward closed first-order definable team properties. In the second part of the talk, we define a system of natural deduction for FOT, and show that it is sound and complete. We also discuss some applications of our logic. In particular, we demonstrate that Arrow’s Theorem in social choice can be formalized in FOT, and Armstrong’s axioms for functional dependencies in database theory can be derived in our system of FOT. (This talk is based on joint work with Juha Kontinen.) Hope to see you there! The LIRa team

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LIRa Session: Kaibo Xie
by LIRa Seminar 01 May '19

01 May '19

Dear all, Tomorrow we will have our next LIRa session. Please find the details below. Speaker: Kaibo Xie (ILLC) Date and Time: Thursday, May 2nd 2019, 16:30-18:00 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: A non-strict-interventionist account for nested counterfactuals. Abstract. Halpern and Pearl provide a way to characterize the meaning of counterfactuals by causal models. But their semantics only accounts for non-nested counterfactuals. A lot of literature has investigated the semantics of nested-counterfactuals based on causal modelling, e.g. Briggs (2012). However, many of those approaches have assumed that the value of the antecedent variables should be independent of the values of their parents in any causal intervention, which is called ``the strict-interventionist condition\'\' by Fisher. Fisher shows that there is a problem inherent to all semantic theories with the strict interventionist condition, which is brought out via a class of counterexamples. The talk will provide semantics for right-nested counterfactuals without assuming the ``strict-interventionist condition\'\', while it does not change Halpern and Briggs\' underlying idea. Hope to see many of you there! The LIRa team

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ILLC-LIRa May 2019