ILLC-LIRa February 2018

illc-lira@list.uva.nl

1 participants
5 discussions

Thursday session with Jana Wagemaker
by LIRa Seminar 27 Feb '18

27 Feb '18

Dear all, This Thursday we will have our next LIRa session. Speaker: Jana Wagemaker Date and Time: Thursday, March 1st 2018, 16:00-17:30 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: Gossip in NetKAT. Abstract. In this talk I will discuss my MoL thesis, where I combined the study of NetKAT with the study of dynamic gossip. NetKAT is a sound and complete network programming language based on Kleene algebra with tests, originally used to describe packets traveling through networks. It has a coalgebraic decision procedure deciding NetKAT equivalences. Dynamic gossip is a field in which it is studied how information spreads through a gossip graph, where the links in the gossip graph are changeable (dynamic). So far no sound and complete logic is available that describes dynamic gossip in a satisfactory way. In this talk we will discuss NetKAT in detail, and then explore the application of NetKAT to dynamic gossip. We will see that a change of perspective on NetKAT in which we keep track of the state of the switches in a network allows us to use NetKAT to model the Learn New Secrets Protocol, which is one of many gossip protocols. The addition to NetKAT to keep track of the state of switches is formalized and shown to remain sound and complete with respect to the packet-processing model. It is shown that the Dynamic Gossip notions of weak successfulness, strong successfulness and sun graph are formalizable in NetKAT and that an important theorem from Dynamic Gossip is also a theorem of NetKAT. Hope to see you there! The LIRa team

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Thursday Session: Dominik Klein
by LIRa Seminar 19 Feb '18

19 Feb '18

Dear all, This Thursday we will have our next LIRa session. Speaker: Dominik Klein (University of Bayreuth) Date and Time: Thursday, February 22nd 2018, 16:00-17:30 Venue: KdVI Seminar Room F3.20, Science Park 107. Title: In the Long Run we’re all Dead: On Kripke Models, Iterated Updates and Dynamic Systems. Abstract. In this talk, we explore the universe of iterated product updates. The talk has two main components. In the first part, we show how iterated product updates can be understood as a dynamic system. In particular, we equip the space of Kripke models with a metric and prove the resulting topology compact. We then show that product updates are continuous with respect to this metric, allowing to understand iterated updates as a discrete time dynamical systems. In the second part of the talk, we apply this apparatus to the case of iterated updates with one and the same event model. There, we expand on a result by Sadzik (2006) that answered a hypothesis by Johan van Benthem to the negative. Sadzik showed that there are pairs of a Kripke Model M and an event model E, such that the process of repeatedly updating M with E never stabilizes nor becomes cyclic. Using our metric based apparatus, we show that Sadzik’s example does, however, stabilize in the infinite, i.e. that the sequence converges to a unique limit point. In fact, we determine a set of conditions on E, the event model, under which iterated update converges in the limit. Finally, we show that Sadzik’s result has an infinite counterpart: There are event models E that, when iteratedly applied to a suitable Kripke model M, display nontrivial limit behavior. They do not converge to a single point nor a limit cycle in the infinite. This is joint work with Rasmus Rendsvig. Hope to see you there! The LIRa team

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Thursday LIRa Session with Alessandro Giordani
by LIRa Seminar 14 Feb '18

14 Feb '18

Dear all, Tomorrow we will have our next LIRa session. Speaker: Alessandro Giordani (Catholic University of Milan) Date and Time: Thursday, February 15th 2018, 16:30-18:00 Venue: KdVI Seminar Room F3.20, Science Park 107. Title: Contrastive Epistemic Logic. Abstract. In standard epistemic logic we assume that knowledge at a world w can be represented as a set E(w) of epistemic scenarios, the ones that are indistinguishable by virtue of the agent’s body of evidence, and that a proposition is known at w provided that all the scenarios in this set are worlds in which that proposition holds, that is E(w) ⊆ [p], where [p] is the set of scenarios where p holds. This immediately implies that knowledge is closed under logical implication, so that it is impossible for an agent to know that p without knowing all the logical consequences of p. Both the basic semantic idea and the closure principle are put into question in contemporary epistemology since, if knowledge is defined along these lines, we can hardly know something, being typically unable to rule out all the epistemic scenarios in which a proposition is false. As a consequence, within the current epistemological debate the idea is explored that an agent can know a proposition even if her evidence set E(w) is not included in [p]. One of the prominent standpoints in this debate is Contrastivism: the position according to which to know that p coincides with knowing that this proposition is the correct answer to a certain question against a set of alternative answers, so that to know is to know the answer to a context-defining question. In the present talk I propose a coherent system of contrastive epistemic logic and show how it can be used to assess the main contrastivist thesis concerning the essence of knowledge. Hope to see you there! The LIRa team

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Thursday LIRa Session: Alessandro Giordani
by LIRa Seminar 12 Feb '18

12 Feb '18

Dear all, This Thursday we will have our next LIRa session. Speaker: Alessandro Giordani (Catholic University of Milan) Date and Time: Thursday, February 15th 2018, 16:30-18:00 Venue: KdVI Seminar Room F3.20, Science Park 107. Title: Contrastive Epistemic Logic. Abstract. In standard epistemic logic we assume that knowledge at a world w can be represented as a set E(w) of epistemic scenarios, the ones that are indistinguishable by virtue of the agent’s body of evidence, and that a proposition is known at w provided that all the scenarios in this set are worlds in which that proposition holds, that is E(w) ⊆ [p], where [p] is the set of scenarios where p holds. This immediately implies that knowledge is closed under logical implication, so that it is impossible for an agent to know that p without knowing all the logical consequences of p. Both the basic semantic idea and the closure principle are put into question in contemporary epistemology since, if knowledge is defined along these lines, we can hardly know something, being typically unable to rule out all the epistemic scenarios in which a proposition is false. As a consequence, within the current epistemological debate the idea is explored that an agent can know a proposition even if her evidence set E(w) is not included in [p]. One of the prominent standpoints in this debate is Contrastivism: the position according to which to know that p coincides with knowing that this proposition is the correct answer to a certain question against a set of alternative answers, so that to know is to know the answer to a context-defining question. In the present talk I propose a coherent system of contrastive epistemic logic and show how it can be used to assess the main contrastivist thesis concerning the essence of knowledge. Hope to see you there! The LIRa team

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Change to Room F3.20 our LIRa Session with Paul Dekker
by LIRa Seminar 01 Feb '18

01 Feb '18

Dear all, Today\'s LIRA session will be at ROOM F3.20. Speaker: Paul Dekker Date and Time: Thursday, February 1st 2018, 16:00-17:30 Venue: ILLC Seminar Room F3.20, Science Park 107. Title: Exclusively Indexical Predicate Logic. Abstract. In this talk I propose a way of redoing classical extensional logic in order to enable a better understanding of dynamic and intensional logic. I first present a propositional logic with only one operator of exclusion, and I then extend it to give a sound and complete characterization of the dynamic declaration of discourse referents and the essentially indexical means to refer back to them. We thus arrive at a parsimonious logic for \"dynamic\" languages like that of Discourse Representation Theory and Dynamic Predicate Logic, but also for computationally attractive languages employing typed feature structures and lexical frame templates. The system moreover holds promise for the proper treatment of names in intensional contexts. Hope to see you there! The LIRa team

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ILLC-LIRa February 2018