ILLC-LIRa September 2018

illc-lira@list.uva.nl

1 participants
7 discussions

LIRa Session: Zoi Terzopoulou
by LIRa Seminar 26 Sep '18

26 Sep '18

Dear all, Tomorrow we will have our next LIRa session. Please, find the details below: Speaker: Zoi Terzopoulou Date and Time: Thursday, September 27th 2018, 16:30-18:00 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: Aggregating Incomplete Pairwise Preferences by Weight. Abstract. Within the area of Computational Social Choice, we develop a model for the aggregation of preferences that do not need to be either complete or transitive. Our focus is on the normative characterisation of aggregation rules under which each agent has a weight that depends only on the size of her ballot, i.e., on the number of pairs of alternatives for which she chooses to report a relative ranking. We show that for rules that satisfy a restricted form of majoritarianism these weights in fact must be constant, while for rules that are invariant under agents with compatible preferences forming pre-election pacts it must be the case that an agent’s weight is inversely proportional to the size of her ballot. The talk is based on joint work with Ulle Endriss, and will not require any background on Computational Social Choice. Hope to see you there! The LIRa team

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LIRa Session: Zoi Terzopoulou
by LIRa Seminar 21 Sep '18

21 Sep '18

Dear all, The next LIRa session will take place on Thursday, September 27th. Our speaker is Zoi Terzopoulou. Please, find the details below: Speaker: Zoi Terzopoulou Date and Time: Thursday, September 27th 2018, 16:30-18:00 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: Aggregating Incomplete Pairwise Preferences by Weight. Abstract. Within the area of Computational Social Choice, we develop a model for the aggregation of preferences that do not need to be either complete or transitive. Our focus is on the normative characterisation of aggregation rules under which each agent has a weight that depends only on the size of her ballot, i.e., on the number of pairs of alternatives for which she chooses to report a relative ranking. We show that for rules that satisfy a restricted form of majoritarianism these weights in fact must be constant, while for rules that are invariant under agents with compatible preferences forming pre-election pacts it must be the case that an agent’s weight is inversely proportional to the size of her ballot. The talk is based on joint work with Ulle Endriss, and will not require any background on Computational Social Choice. Hope to see you there! The LIRa team

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LIRa Session: Gianluca Grilletti
by LIRa Seminar 19 Sep '18

19 Sep '18

Dear all, This is a reminder of tomorrow\'s LIRa session. Please, find the details below: Speaker: Gianluca Grilletti Date and Time: Thursday, September 20th 2018, 16:30-18:00 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: An Ehrenfeucht-Fraïssé Game for InqBQ. Abstract. InqBQ [1] is a first-order version of inquisitive logic, encompassing both questions and quantifiers. Questions like ``What is an element with property P?’’ and ``What is the extension of property P?\'\' can be represented using the usual logical operators from first-order logic in addition to the inquisitive counterpart of classical disjunction and classical existential quantifier respectively. Several questions about InqBQ remain open: Is the entailment of the logic axiomatizable? Does the entailment between questions boil down to some dependency between the statements supporting the questions? Which questions are expressible and which are not expressible? Ehrenfeucht-Fraïssé games [2,4] proved to be a valuable tool to study the expressive power of several logics [3,5,8]. The main idea is to characterize logical equivalence between models, w.r.t. the whole logic or certain fragments of it, using game-theoretic tools; this in turn gives a strategy to prove that certain properties of models -- e.g. the finiteness of the domain in first-order logic -- are not expressible, namely by finding a winning strategy in a suitable game. In this talk I will present an EF-game for InqBQ and the corresponding characterization theorem. I will apply the result obtained to show that certain natural questions -- e.g. “How many elements have property P?” -- are not expressible by InqBQ formulas. (This is joint work with Ivano Ciardelli.) References [1] Ivano Ciardelli. Questions in logic. PhD thesis, Institute for Logic, Language and Computation, University of Amsterdam, 2016. [2] Andrzej Ehrenfeucht. An application of games to the completeness problem for formalized theories. Journal of Symbolic Logic, 32(2):281–282, 1967. [3] Ronald Fagin. Monadic Generalized Spectra. Zeitschrift für mathematische Logik und Grundlagen der Mathematik, 21:89–96, 1975. [4] Roland Fraïssé. Sur quelques classifications des systèmes de relations. Publications Scientifiques de l’Université D’Alger, 1(1):35–182, June 1954. [5] Neil Immerman. Upper and lower bounds for first order expressibility. Journal of Com- puter and System Sciences, 25(1):76–98, 1982. [6] Jouko Väänänen. Models and Games. Cambridge University Press, New York, NY, USA, 1st edition, 2011. Hope to see you there! The LIRa team

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LIRa Session: Gianluca Grilletti
by LIRa Seminar 14 Sep '18

14 Sep '18

Dear all, The next LIRa session will take place on Thursday, September 20th. Our speaker is Gianluca Grilletti. Please, find the details below: Speaker: Gianluca Grilletti Date and Time: Thursday, September 20th 2018, 16:30-18:00 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: An Ehrenfeucht-Fraïssé Game for InqBQ. Abstract. InqBQ [1] is a first-order version of inquisitive logic, encompassing both questions and quantifiers. Questions like ``What is an element with property P?’’ and ``What is the extension of property P?\'\' can be represented using the usual logical operators from first-order logic in addition to the inquisitive counterpart of classical disjunction and classical existential quantifier respectively. Several questions about InqBQ remain open: Is the entailment of the logic axiomatizable? Does the entailment between questions boil down to some dependency between the statements supporting the questions? Which questions are expressible and which are not expressible? Ehrenfeucht-Fraïssé games [2,4] proved to be a valuable tool to study the expressive power of several logics [3,5,8]. The main idea is to characterize logical equivalence between models, w.r.t. the whole logic or certain fragments of it, using game-theoretic tools; this in turn gives a strategy to prove that certain properties of models -- e.g. the finiteness of the domain in first-order logic -- are not expressible, namely by finding a winning strategy in a suitable game. In this talk I will present an EF-game for InqBQ and the corresponding characterization theorem. I will apply the result obtained to show that certain natural questions -- e.g. “How many elements have property P?” -- are not expressible by InqBQ formulas. (This is joint work with Ivano Ciardelli.) References [1] Ivano Ciardelli. Questions in logic. PhD thesis, Institute for Logic, Language and Computation, University of Amsterdam, 2016. [2] Andrzej Ehrenfeucht. An application of games to the completeness problem for formalized theories. Journal of Symbolic Logic, 32(2):281–282, 1967. [3] Ronald Fagin. Monadic Generalized Spectra. Zeitschrift für mathematische Logik und Grundlagen der Mathematik, 21:89–96, 1975. [4] Roland Fraïssé. Sur quelques classifications des systèmes de relations. Publications Scientifiques de l’Université D’Alger, 1(1):35–182, June 1954. [5] Neil Immerman. Upper and lower bounds for first order expressibility. Journal of Com- puter and System Sciences, 25(1):76–98, 1982. [6] Jouko Väänänen. Models and Games. Cambridge University Press, New York, NY, USA, 1st edition, 2011. Hope to see you there! The LIRa team

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Lira Session: Jules Hedges
by LIRa Seminar 12 Sep '18

12 Sep '18

Dear all, This is a reminder for tomorrow\'s LIRa session. Please, find the details below: Speaker: Jules Hedges Date and Time: Thursday, September 13th 2018, 16:30-18:00 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: Compositional Game Theory. Abstract. Open games are a foundation of non-cooperative game theory that is strongly compositional: all games are built from small pieces using sequential and parallel composition operators. They also come for free with an intuitive but formal graphical language that allows visualising the information flow inside a game. I will focus on the foundations, which involves a careful analysis of how observable and counterfactual information interact in a game. Time permitting I’ll briefly discuss a linguistic application, building language-games recursively on a categorial grammar (work in progress with Martha Lewis). This talk necessarily involves some category theory, but I’ll try to be as gentle as possible. Hope to see you there! The LIRa team

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Lira Session: Jules Hedges
by LIRa Seminar 07 Sep '18

07 Sep '18

Dear all, We are very happy to announce that next Thursday, we will have our first LIRa session for this academic year. Our regular time slot will be Thursday 16:30 - 18.00 (NB: from November onward, the seminar will start at 17:00), followed by drinks at the common room. We hope to see many of you there! Below you can find the details of the upcoming session: Speaker: Jules Hedges Date and Time: Thursday, September 13th 2018, 16:30-18:00 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: Compositional Game Theory. Abstract. Open games are a foundation of non-cooperative game theory that is strongly compositional: all games are built from small pieces using sequential and parallel composition operators. They also come for free with an intuitive but formal graphical language that allows visualising the information flow inside a game. I will focus on the foundations, which involves a careful analysis of how observable and counterfactual information interact in a game. Time permitting I’ll briefly discuss a linguistic application, building language-games recursively on a categorial grammar (work in progress with Martha Lewis). This talk necessarily involves some category theory, but I’ll try to be as gentle as possible. The LIRa team

1 0

Lira Session: Jules Hedges
by LIRa Seminar 07 Sep '18

07 Sep '18

Dear all, Speaker: Jules Hedges Date and Time: Thursday, September 13th 2018, 16:30-18:00 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: Compositional Game Theory. Abstract. Open games are a foundation of non-cooperative game theory that is strongly compositional: all games are built from small pieces using sequential and parallel composition operators. They also come for free with an intuitive but formal graphical language that allows visualising the information flow inside a game. I will focus on the foundations, which involves a careful analysis of how observable and counterfactual information interact in a game. Time permitting I’ll briefly discuss a linguistic application, building language-games recursively on a categorial grammar (work in progress with Martha Lewis). This talk necessarily involves some category theory, but I’ll try to be as gentle as possible. The LIRa team

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ILLC-LIRa September 2018