Sophia Knight

Arbitrary Announcements on Topological Subset Spaces

Subset space semantics for public announcement logic in the spirit of the effort modality have been proposed by Wang and Agotnes [18] and by Bjorndahl [6]. They propose to model the public announcement modality by shrinking the epistemic range with respect to which a postcondition of the announcement is evaluated, instead of by restricting the model to the set of worlds satisfying the announcement. Thus we get an “elegant, model-internal mechanism for interpreting public announcements” [6, p. 12]. In this work, we extend Bjorndahl’s logic \(PAL_{int}\) of public announcement, which is modelled on topological spaces using subset space semantics and adding the interior operator, with an arbitrary announcement modality, and we provide topological subset space semantics for the corresponding arbitrary announcement logic \(APAL_{int}\), and demonstrate completeness of the logic by proving that it is equal in expressivity to the logic without arbitrary announcements, employing techniques from [2, 13].

Partial Information and Uniform Strategies

We present an alternating-time temporal epistemic logic with uniform strategies, interpreted in a novel way on transition systems for modelling situations in which agents with partial information interact to determine the way the system updates. This logic uATEL allows us to model what properties agents can enforce when they act according to strategies based on their knowledge. Apart from the usual memoryless strategies, we distinguish state-based memory, where agents recall the history of previous states, from perfect recall, where agents also recall their actions. We show that this makes a difference. Our logic includes three strategic operators for groups, representing the case where all the agents in the group cooperate actively, but do not share their knowledge, the case where some agents in the group may be passive, and the case where all the agents in the group share their knowledge. We include a detailed comparison to the literature on the subject.

Bisimulation for Markov Decision Processes through Families of Functional Expressions

We transfer a notion of quantitative bisimilarity for labelled Markov processes [1] to Markov decision processes with continuous state spaces. This notion takes the form of a pseudometric on the system states, cast in terms of the equivalence of a family of functional expressions evaluated on those states and interpreted as a real-valued modal logic. Our proof amounts to a slight modification of previous techniques [2,3] used to prove equivalence with a fixed-point pseudometric on the state-space of a labelled Markov process and making heavy use of the Kantorovich probability metric. Indeed, we again demonstrate equivalence with a fixed-point pseudometric defined on Markov decision processes [4] ; what is novel is that we recast this proof in terms of integral probability metrics [5] defined through the family of functional expressions, shifting emphasis back to properties of such families. The hope is that a judicious choice of family might lead to something more computationally tractable than bisimilarity whilst maintaining its pleasing theoretical guarantees. Moreover, we use a trick from descriptive set theory to extend our results to MDPs with bounded measurable reward functions, dropping a previous continuity constraint on rewards and Markov kernels.

Reasoning about knowledge and messages in asynchronous multi-agent systems

We propose a variant of public announcement logic for asynchronous systems. To capture asynchrony, we introduce two different modal operators for sending and receiving messages. The natural approac ...

Preface for the special issue on Interaction and Concurrency Experience 2014

This special issue contains extended versions of selected papers from the 7th Interaction and Concurrency Experience workshop (ICE 2014). The workshop was held in Berlin (Germany) on June 6th, 2014. ICE workshops form a series of international scientific meetings oriented to theoretical computer science researchers with special interest in models, verification, tools, and programming primitives for complex interactions. The general scope of the venue includes theoretical and applied aspects of interactions and the synchronization mechanisms used among components of concurrent/distributed systems, related to several areas of computer science in the broad spectrum ranging from formal specification and analysis to studies inspired by emerging computational models. The authors of the most prominent papers presented at ICE 2014 were invited to submit an extended version to this special issue. In order to guarantee the fairness and quality of the selection process, each submission received at least three reviews. The review process has also ensured that the accepted articles significantly extend and improve the original workshop contributions. This special issue features three articles: • Declarative event based models of concurrency and refinement in psi-calculi, by Hakon Normann, Christian Johansen and Thomas Hildebrandt. In this paper the authors show an exploration of declarative event-based specifications open to runtime refinement aiming at a declarative model with support for adaptation. • Contracts as games on event structures, by Massimo Bartoletti, Tiziana Cimoli, G. Michele Pinna and Roberto Zunino. This work presents an event structure based interpretation of contracts, allowing to study the rights and obligations of contract participants in a natural setting. • Relating two automata-based models of orchestration and choreography, by Davide Basile, Pierpaolo Degano, Gian Luigi Ferrari and Emilio Tuosto. This paper presents a comparison between local contract-based specifications coordinated by orchestrators with communicating machines that have decentralized coordination. We want to thank all the authors who contributed to this volume. We would like to thank all the members of the Program Committee of ICE, who helped us in the selection of the papers and who helped the authors to improve their contributions in several ways. Additional referees were involved in the review of the papers invited for this special issue and we thank their timely contributions. We would also like to thank the editors of JLAMP, for their support during the whole editorial process.

Announcement as effort on topological spaces

We propose a multi-agent logic of knowledge, public and arbitrary announcements, that is interpreted on topological spaces in the style of subset space semantics. The arbitrary announcement modality functions similarly to the effort modality in subset space logics, however, it comes with intuitive and semantic differences. We provide axiomatizations for three logics based on this setting, and demonstrate their completeness.

Asynchronous Announcements in a Public Channel

We propose a variant of public announcement logic for asynchronous systems. We give a syntax where sending and receiving messages are modeled by different modal operators. The natural approach to defining the semantics leads to a circular definition, but we describe two restricted cases in which we solve this problem. The first case requires the Kripke model representing the initial epistemic situation to be a finite tree, and the second one only allows announcements from the existential fragment. Finally, we provide complexity results for the model checking problem.

Proceedings Fourth Interaction and Concurrency Experience

This volume contains the proceedings of ICE 2014, the 7th Interaction and Concurrency Experience, which was held in Berlin, Germany on the 6th of June 2014 as a satellite event of DisCoTec 2014. The ICE procedure for paper selection allows PC members to interact, anonymously, with authors. During the review phase, each submitted paper is published on a Wiki and associated with a discussion forum whose access is restricted to the authors and to all the PC members not declaring a conflict of interests. The PC members post comments and questions that the authors reply to. Each paper was reviewed by three PC members, and altogether 8 papers (including 3 short papers) were accepted for publication. We were proud to host two invited talks, by Pavol Cerny and Kim Larsen, whose abstracts are included in this volume together with the regular papers.