ILLC-LIRa

illc-lira@list.uva.nl

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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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LIRa Session: Kees van Deemter
by LIRa Seminar 24 Apr '19

24 Apr '19

Dear all, Tomorrow we will have our next LIRa session. Please, find the details below: Speaker: Kees van Deemter (Utrecht University and University of Aberdeen) Date and Time: Thursday, April 25th 2019, 16:30-18:00 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: The Elusive Benefits of Vagueness. Abstract. Much of everyday language is vague, yet the benefits of vagueness for hearers and readers are proving to be elusive. We discuss a range of earlier controlled experiments with human participants, and we report on a new series of experiments that we conducted in recent years. These new experiments, which focus on strategic use of vague expressions that are part of referential noun phrases, aim to separate the utility of vagueness (defined by the existence of borderline cases, as is common in theoretical work) from other factors that tend to co-occur with vagueness. Having presented the evidence, we argue that the evidence supports a view of vagueness where the benefits of vague terms are due to other influences, rather than to vagueness itself. These factors include: low granularity; the use of evaluative words; the avoidance of overtly numerical words; the existence of comparison strategies; and, lastly and more tentatively, a phenomenon that we call range reduction. Although it is possible that other types of vague expressions (i.e., outside referential noun phrases) behave differently, our work suggests that vagueness itself may not increase the utility of an expression at all. This is joint work with Matthew Green (Bournemouth University). Hope to see you there! The LIRa team

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