ILLC-LIRa

illc-lira@list.uva.nl

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LIRa Session: Raul Fervari
by LIRa Seminar 25 Sep '19

25 Sep '19

Dear all, Tomorrow we will have our next LIRa session. Please, find the details below: Speaker: Raul Fervari (Universidad Nacional de Córdoba) Date and Time: Thursday, September 26th 2019, 16:30-18:00 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: Separation logics: a modal perspective. Abstract. Modal separation logics (MSL) are formalisms that have been recently proposed combining modal operators with separating connectives, both interpreted over one-dimensional Kripke models. In this way, MSL can be seen either as separation logics enriched with local operations to reason about memory states of a piece of software, or either as modal logics with global relation-changing operators (á la sabotage logic). In this talk we will present MSL and some of its most interesting fragments, and discuss some results about complexity, axiom systems and expressivity. We will conclude by discussing some ongoing and future lines of research. Some references: [1] S. Demri and R. Fervari. On the Complexity of Modal Separation Logics. In Proceedings of Advances in Modal Logics AiML’18, pages 179-198. College Publications, 2018. [2] S. Demri, R. Fervari and A. Mansutti. Axiomatising Logics with Separating Conjunction and Modalities. In Proceedings of the 16th European Conference on Logics in Artificial Intelligence (JELIA 2019). Hope to see you there! The LIRa team

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LIRa Session: Raul Fervari
by LIRa Seminar 20 Sep '19

20 Sep '19

Dear all, We will have our next session on Thursday, September 26th. Our speaker is Raul Fervari, and you can find the details of the talk below: Speaker: Raul Fervari (Universidad Nacional de Córdoba) Date and Time: Thursday, September 26th 2019, 16:30-18:00 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: Separation logics: a modal perspective. Abstract. Modal separation logics (MSL) are formalisms that have been recently proposed combining modal operators with separating connectives, both interpreted over one-dimensional Kripke models. In this way, MSL can be seen either as separation logics enriched with local operations to reason about memory states of a piece of software, or either as modal logics with global relation-changing operators (á la sabotage logic). In this talk we will present MSL and some of its most interesting fragments, and discuss some results about complexity, axiom systems and expressivity. We will conclude by discussing some ongoing and future lines of research. Some references: [1] S. Demri and R. Fervari. On the Complexity of Modal Separation Logics. In Proceedings of Advances in Modal Logics AiML’18, pages 179-198. College Publications, 2018. [2] S. Demri, R. Fervari and A. Mansutti. Axiomatising Logics with Separating Conjunction and Modalities. In Proceedings of the 16th European Conference on Logics in Artificial Intelligence (JELIA 2019). Hope to see you there! The LIRa team

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LIRa Session: Erman Acar
by LIRa Seminar 18 Sep '19

18 Sep '19

Dear all, Tomorrow we will have our next LIRa session. Please, find the details below: Speaker: Erman Acar (VU Amsterdam) Date and Time: Thursday, September 19th 2019, 16:30-18:00 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: When Satisfiability is easier than Model Checking: A Fragment of Strategy Logic. Abstract. In the design of complex systems, model-checking and satisfiability arise as two prominent decision problems. While model-checking requires the designed system to be provided in advance, satisfiability allows to check if such a system even exists. With very few exceptions, the second problem turns out to be harder than the first one from a complexity-theoretic point of view. In this talk, I will present a recent work which investigates the connection between the two problems for a non-trivial fragment of Strategy Logic (SL) which extends Linear Temporal Logic with first-order quantifications over strategies, thus allowing to explicitly reason about the strategic abilities of agents in a multi-agent system. The SL fragment we consider is obtained by preventing strategic quantifications within the scope of temporal operators. The resulting logic is quite powerful, still allowing to express important game-theoretic properties of multi-agent systems, such as existence of Nash and immune equilibria, as well as to formalise the rational synthesis problem. It turns out that satisfiability for such a fragment is PSPACE-COMPLETE, while its model-checking complexity is 2EXPTIME-HARD. The result is obtained by means of an elegant encoding of the problem into the satisfiability of conjunctive-binding first-order logic, a recently discovered decidable fragment of first-order logic. This is a joint work with Massimo Benerecetti and Fabio Mogavero. Hope to see you there! The LIRa team

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LIRa Session: Erman Acar
by LIRa Seminar 13 Sep '19

13 Sep '19

Dear all, We will have our next session on Thursday, September 19th 2019. Our speaker is Erman Acar and you can find the details of the talk below: Speaker: Erman Acar (VU Amsterdam) Date and Time: Thursday, September 19th 2019, 16:30-18:00 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: When Satisfiability is easier than Model Checking: A Fragment of Strategy Logic. Abstract. In the design of complex systems, model-checking and satisfiability arise as two prominent decision problems. While model-checking requires the designed system to be provided in advance, satisfiability allows to check if such a system even exists. With very few exceptions, the second problem turns out to be harder than the first one from a complexity-theoretic point of view. In this talk, I will present a recent work which investigates the connection between the two problems for a non-trivial fragment of Strategy Logic (SL) which extends Linear Temporal Logic with first-order quantifications over strategies, thus allowing to explicitly reason about the strategic abilities of agents in a multi-agent system. The SL fragment we consider is obtained by preventing strategic quantifications within the scope of temporal operators. The resulting logic is quite powerful, still allowing to express important game-theoretic properties of multi-agent systems, such as existence of Nash and immune equilibria, as well as to formalise the rational synthesis problem. It turns out that satisfiability for such a fragment is PSPACE-COMPLETE, while its model-checking complexity is 2EXPTIME-HARD. The result is obtained by means of an elegant encoding of the problem into the satisfiability of conjunctive-binding first-order logic, a recently discovered decidable fragment of first-order logic. This is a joint work with Massimo Benerecetti and Fabio Mogavero. Hope to see you there! The LIRa team

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LIRa session: René Mellema
by LIRa Seminar 11 Sep '19

11 Sep '19

Dear all, Tomorrow we will have our next LIRa session. Please, find the details below: Speaker: René Mellema Date and Time: Thursday, September 12th 2019, 16:30-18:30 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: An Inquisitive Dynamic Epistemic Logic with Factual Change. Abstract. In many situations, we want to model the effect of actions on both the knowledge of others, and also what they want to know afterwards. For example, after you hear something fall in another room, you would not only want to know whether others heard that, but also if they want to know what fell down. In this talk we will present a logic for multi-agent modelling for these kinds of situations by combining two logical frameworks, the Logic of Communication and Change and the newer framework of Inquisitive Semantics. The latter is a framework that has been set up to give a reasonable formal interpretation to questions. From this field we will mostly use ideas from Action Model Logic with Issues. This allows us to build a logic where we can model knowledge, including common knowledge; the questions that agents want an answer to, including questions that are shared between agents; and epistemic events like public and private announcements and factual change, all in one logic. This new logic is based on a new inquisitive epistemic logic for relativized group knowledge which we call Inquisitive Epistemic Propositional Dynamic Logic, based on PDL. We will present a sound and complete axiomatisation for this logic and discuss parts of its completeness proof. We enriched this logic with action models that also represent factual change. We call this resulting logic the Logic of Communication, Change, and Issues. We have shown that this logic can be completely reduced to its underlying static language and has a sound and complete axiomatisation. This talk is based on my MSc thesis, which was done under the supervision of Rineke Verbrugge and Floris Roelofsen. Hope to see you there! The LIRa team

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LIRa session: René Mellema
by LIRa Seminar 06 Sep '19

06 Sep '19

Dear all, LIRa is back! We will have our first session on Thursday, September 12th 2019. The regular slot for this term is 16.30-18.00. Our first speaker is René Mellema and you can find the details of the talk below: Speaker: René Mellema Date and Time: Thursday, September 12th 2019, 16:30-18:30 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: An Inquisitive Dynamic Epistemic Logic with Factual Change. Abstract. In many situations, we want to model the effect of actions on both the knowledge of others, and also what they want to know afterwards. For example, after you hear something fall in another room, you would not only want to know whether others heard that, but also if they want to know what fell down. In this talk we will present a logic for multi-agent modelling for these kinds of situations by combining two logical frameworks, the Logic of Communication and Change and the newer framework of Inquisitive Semantics. The latter is a framework that has been set up to give a reasonable formal interpretation to questions. From this field we will mostly use ideas from Action Model Logic with Issues. This allows us to build a logic where we can model knowledge, including common knowledge; the questions that agents want an answer to, including questions that are shared between agents; and epistemic events like public and private announcements and factual change, all in one logic. This new logic is based on a new inquisitive epistemic logic for relativized group knowledge which we call Inquisitive Epistemic Propositional Dynamic Logic, based on PDL. We will present a sound and complete axiomatisation for this logic and discuss parts of its completeness proof. We enriched this logic with action models that also represent factual change. We call this resulting logic the Logic of Communication, Change, and Issues. We have shown that this logic can be completely reduced to its underlying static language and has a sound and complete axiomatisation. This talk is based on my MSc thesis, which was done under the supervision of Rineke Verbrugge and Floris Roelofsen. Hope to see you there! The LIRa team

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reminder: GROLOG/LIRa Logic Afternoon
by LIRa Seminar 26 Jun '19

26 Jun '19

Dear all, We\'d like to remind you of the GROLOG/LIRa Logic afternoon. Please find the details below: Date and Time: Monday, July 1st 2019, 14:00-17:00 Venue: Room Beta, Faculty of Philosophy, Oude Boteringestraat 52, Groningen. Speaker #1: Roberto Ciuni (University of Padova) Title: Information-based oughts and their interaction with knowledge and belief. Abstract. In this talk, I present a conditional logic that enables us to reason about information-based oughts and the role they play in decision-theoretical scenarios that crucially involve knowledge and beliefs. Unconditional oughts and beliefs turn to be special cases of their conditional counterparts. The paper proceeds as follows. After providing a bit of background and setup, I introduce the notions of an objective ought and an information-based ought, and we present a maximality-based semantics for them and the doxastic notions we deal with, in the style of Hansson, Board, van Benthem, Baltag and Smets. Finally, I present a complete axiom system for the resulting logic. Speaker #2: Louwe Kuijer (University of Liverpool) Title: Minimal rationality constraints for conditional obligation. Abstract. A conditional obligation is of the form O(p|q), with the meaning that p is obligatory under the condition that q is true. We can give semantics to this O operator using a preference relation on states, by saying that O(p|q) holds if p is true on all the \"best\" q states. But of course that does not fully determine the semantics unless we specify what we mean by a state being one of the \"best\". There are several options: we could say that a states is \"best\" if it is maximal (i.e., there is no other state that is strictly preferred) or if it is optimal (i.e., weakly preferred over all other states). Here, we take a different option and say that a state is among the \"best\" states if it is part of at least one so-called minimal retentive set. Defining \"best\" in this way leads to a weak logic for O, but we can find contexts where this weak logic is the appropriate choice. In this talk I will (i) introduce the semantics for O based on minimal retentive sets and give an example, (ii) introduce a sound an complete axiomatization, and discuss how it differs from other axiomatizations of conditional obligations and (iii) briefly discuss the challenges encountered while defining a canonical model for this logic. Speaker #3: Karolina Krzyzanowska (ILLC, University of Amsterdam) Title: True clauses, false connections, and the limits of pragmatic explanations. Abstract. It is a common intuition that the antecedent of an indicative conditional should have something to do with its consequent, that they should be somehow connected. However, only very few theories of conditionals do justice to this intuition. In fact, many prominent accounts of indicative conditionals validate the Principle of Conjunctive Sufficiency that allows to infer a conditional from the truth of its antecedent and the consequent. Consequently, many odd conditionals whose antecedents and consequents are not connected at all are rendered true, or highly acceptable, on these accounts. Their proponents tend to dismiss the oddness of such conditionals as a pragmatic phenomenon, outside the scope of interest of a semanticist or a logician. This is not to say that no pragmatic explanations of the oddity of missing-link conditionals have been proposed. In my talk, I will discuss the most salient of these proposals and I will present empirical data that show how they all fail. The talks will be followed by drinks and dinner with the speakers. For more information about the GROLOG seminar and scheduled events, please check the GROLOG seminar webpage. Hope to see you there! The LIRa team

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DALi extended deadline
by LIRa Seminar 12 Jun '19

12 Jun '19

Dear all, The deadline for DALi has been extended to June 28. For more details, please check: https://projects.illc.uva.nl/lgc/seminar/2019/03/cfp-2nd-dali-dynamic-logic… The LIRa team

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Johan van Benthem Workshop and GROLOG/LIRa afternoon
by LIRa Seminar 10 Jun '19

10 Jun '19

Dear all, We would like to bring two events to your attention. First, the workshop on the occasion of Johan van Benthem’s 70th birthday (on June 12th), and second, the GROLOG/LIRa afternoon (on July 1st) in Groningen. More details can be found below: (1) On 12 June 2019, ILLC is organizing a workshop and reception to celebrate Johan van Benthem\'s 70th birthday. The workshop consists of talks by Johan and some of his many former PhD students at UvA and Stanford, and will be followed by a Reception. Everybody is most welcome to attend, but please send an email to Peter van Ormondt at illc(a)uva.nl if you intend to do so. Date and Time: Wednesday, June 12th 2019, 10:00-16:30 Venue: ILLC Common room, F1.21, Science Park 107. Program: please check the workshop webpage at this link: http://festschriften.illc.uva.nl/J70/ (2) GROLOG/LIRa Logic Afternoon Date and Time: Monday, July 1st 2019, 14:00-16:00 Venue: Room Beta, Faculty of Philosophy, Oude Boteringestraat 52, Groningen. For more information on the talks of GROLOG/LIRa, please check: https://projects.illc.uva.nl/lgc/seminar/2019/06/grolog-lira-logic-afternoo… Hope to see you there! The LIRa team

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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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