Modularity and Openness in Modeling Multi-Agent Systems

We revisit the formalism of modular interpreted systems (MIS) which encourages modular and open modeling of synchronous multi-agent systems. The original formulation of MIS did not live entirely up to its promise. In this paper, we propose how to improve modularity and openness of MIS by changing the structure of interference functions. These relatively small changes allow for surprisingly high flexibility when modeling actual multi-agent systems. We demonstrate this on two well-known examples, namely the trains, tunnel and controller, and the dining cryptographers. Perhaps more importantly, we propose how the notions of multi-agency and openness, crucial for multi-agent systems, can be precisely defined based on their MIS representations.Comment: In Proceedings GandALF 2013, arXiv:1307.416

Refining and Delegating Strategic Ability in ATL

We propose extending Alternating-time Temporal Logic (ATL) by an operator <i refines-to G> F to express that agent i can distribute its powers to a set of sub-agents G in a way which satisfies ATL condition f on the strategic ability of the coalitions they may form, possibly together with others agents. We prove the decidability of model-checking of formulas whose subformulas with this operator as the main connective have the form ...<i_m refines-to G_m> f, with no further occurrences of this operator in f.Comment: In Proceedings SR 2014, arXiv:1404.041

Situation awareness and ability in coalitions

This paper proposes a discussion on the formal links between the Situation Calculus and the semantics of interpreted systems as far as they relate to Higher-Level Information Fusion tasks. Among these tasks Situation Analysis require to be able to reason about the decision processes of coalitions. Indeed in higher levels of information fusion, one not only need to know that a certain proposition is true (or that it has a certain numerical measure attached), but rather needs to model the circumstances under which this validity holds as well as agents' properties and constraints. In a previous paper the authors have proposed to use the Interpreted System semantics as a potential candidate for the unification of all levels of information fusion. In the present work we show how the proposed framework allow to bind reasoning about courses of action and Situation Awareness. We propose in this paper a (1) model of coalition, (2) a model of ability in the situation calculus language and (3) a model of situation awareness in the interpreted systems semantics. Combining the advantages of both Situation Calculus and the Interpreted Systems semantics, we show how the Situation Calculus can be framed into the Interpreted Systems semantics. We illustrate on the example of RAP compilation in a coalition context, how ability and situation awareness interact and what benefit is gained. Finally, we conclude this study with a discussion on possible future works

Reducing model checking commitments for agent communication to model checking ARCTL and GCTL*

Social commitments have been extensively and effectively used to represent and model business contracts among autonomous agents having competing objectives in a variety of areas (e.g., modeling business processes and commitment-based protocols). However, the formal verification of social commitments and their fulfillment is still an active research topic. This paper presents CTLC+ that modifies CTLC, a temporal logic of commitments for agent communication that extends computation tree logic (CTL) logic to allow reasoning about communicating commitments and their fulfillment. The verification technique is based on reducing the problem of model checking CTLC+ into the problem of model checking ARCTL (the combination of CTL with action formulae) and the problem of model checking GCTL* (a generalized version of CTL* with action formulae) in order to respectively use the extended NuSMV symbolic model checker and the CWB-NC automata-based model checker as a benchmark. We also prove that the reduction techniques are sound and the complexity of model checking CTLC+ for concurrent programs with respect to the size of the components of these programs and the length of the formula is PSPACE-complete. This matches the complexity of model checking CTL for concurrent programs as shown by Kupferman et al. We finally provide two case studies taken from business domain along with their respective implementations and experimental results to illustrate the effectiveness and efficiency of the proposed technique. The first one is about the NetBill protocol and the second one considers the Contract Net protocol

Model checking and compositional reasoning for multi-agent systems

Multi-agent systems are distributed systems containing interacting autonomous agents designed to achieve shared and private goals. For safety-critical systems where we wish to replace a human role with an autonomous entity, we need to make assurances about the correctness of the autonomous delegate. Specialised techniques have been proposed recently for the verification of agents against mentalistic logics. Problematically, these approaches treat the system in a monolithic way. When verifying a property against a single agent, the approaches examine all behaviours of every component in the system. This is both inefficient and can lead to intractability: the so-called state-space explosion problem. In this thesis, we consider techniques to support the verification of agents in isolation. We avoid the state-space explosion problem by verifying an individual agent in the context of a specification of the rest of the system, rather than the system itself. We show that it is possible to verify an agent against its desired properties without needing to consider the behaviours of the remaining components. We first introduce a novel approach for verifying a system as a whole against specifications expressed in a logic of time and knowledge. The technique, based on automata over trees, supports an efficient procedure to verify systems in an automata-theoretic way using language containment. We show how the automata-theoretic approach can be used as an underpinning for assume-guarantee reasoning for multi-agent systems. We use a temporal logic of actions to specify the expected behaviour of the other components in the system. When performing modular verification, this specification is used to exclude behaviours that are inconsistent with the concrete system. We implement both approaches within the open-source model checker MCMAS and show that, for the relevant properties, the assume-guarantee approach can significantly increase the tractability of individual agent verification.Open Acces