Colloquium Loria – CELLO team
Next Colloquium will take place on Tuesday, 20th April at 1:30 pm on Teams.
We are glad to welcome the CELLO team, with presentations given by our colleagues Hans van Ditmarsch, Marta Gawek and Mo Liu.
Program and abstracts:
13:30 – 14:00
- speaker: Hans van Ditmarsch, CELLO @ LORIA
- title: Knowledge and simplicial complexes
- abstract: Simplicial complexes are a versatile and convenient paradigm on which to build all the tools and techniques of the logic of knowledge, on the assumption that initial epistemic models can be described in a distributed fashion. Thus, we can define: knowledge, belief, bisimulation, the group notions of mutual, distributed and common knowledge, and also dynamics in the shape of simplicial action models. We give a survey on how to interpret all such notions on simplicial complexes, building upon the foundations laid in prior work by Goubault et al. More recent work investigates so-called impure simplicial complexes, that also take into account crashed processes.
 Hans van Ditmarsch, Eric Goubault, Jérémy Ledent, and Sergio Rajsbaum. Knowledge and simplicial complexes. To appear. CoRR abs/2002.08863, 2020.
 Hans van Ditmarsch. Wanted Dead or Alive: Epistemic logic for impure simplicial complexes. CoRR abs/2103.03032, 2021.
Joint work with Éric Goubault, Jérémy Ledent, and Sergio Rajsbaum.
14:00 – 14:30
- speaker: Marta Gawek, CELLO @ LORIA
- title: An epistemic separation logic with action models
- abstract: We investigate extensions of separation logic with epistemic and dynamic epistemic modalities. Separation logics are based on the intuitionistic logic of bunched implications (BI) or its classical counterpart Boolean BI. These logics combine additive and multiplicative connectives in the language, expressing the notions of resource composition and resource decomposition. Epistemic Separation Logic with Action Models (ESLAM) is a generalization of the Public Announcement Separation Logic (PASL) of Courtault et al. We present the syntax and semantics of ESLAM as well as reduction axioms for the elimination of dynamic modalities.
References:  Jean-René Courtault, Hans van Ditmarsch, and Didier Galmiche. A Public Announcement Separation Logic. Mathematical Structures in Computer Science 29(6):828–871, 2019.
 David Pym. The Semantics and Proof Theory of the Logic of Bunched Implications, Springer, 2002.
 Hans van Ditmarsch, Didier Galmiche, and Marta Gawek. An Epistemic Separation Logic with Action Models. Proceedings of 9th ICLA, 2021.Joint work with Hans van Ditmarsch and Didier Galmiche.
14:30 – 15:00
- speaker: Mo Liu, CELLO @ LORIA
- title: Expressivity of some versions of APAL
- abstract: Arbitrary public announcement logic (APAL) is a logic of change of knowledge with modalities representing quantification over announcements. It extends public announcement logic (PAL). We present three rather different versions of APAL: FSAPAL only quantifies over announcements containing a finite subset of all propositional variables. SCAPAL only quantifies over announcements containing variables occurring in the formula bound by the quantifier. IPAL quantifies over announcements implying a given formula. We determine the relative expressivity of FSAPAL, SCAPAL and IPAL in relation to APAL and PAL.
 Hans van Ditmarsch, Mo Liu, Louwe B. Kuijer, and Igor Sedlár. Expressivity of Some Versions of APAL. Proceedings of DaLí 2020, pp 120-136, 2020.
Joint work with Hans van Ditmarsch, Louwe B. Kuijer, and Igor Sedlár.