3,370 research outputs found
Bounded Model Checking for Linear Time Temporal-Epistemic Logic
We present a novel approach to the verification of multi-agent systems using bounded model checking for specifications in LTLK, a linear time temporal-epistemic logic. The method is based on binary decision diagrams rather than the standard conversion to Boolean satisfiability. We apply the approach to two classes of interpreted systems: the standard, synchronous semantics and the interleaved semantics. We provide a symbolic algorithm for the verification of LTLK over models of multi-agent systems and evaluate its implementation against MCK, a competing model checker for knowledge. Our evaluation indicates that the interleaved semantics can often be preferable in the verification of LTLK
Verification of Agent-Based Artifact Systems
Artifact systems are a novel paradigm for specifying and implementing
business processes described in terms of interacting modules called artifacts.
Artifacts consist of data and lifecycles, accounting respectively for the
relational structure of the artifacts' states and their possible evolutions
over time. In this paper we put forward artifact-centric multi-agent systems, a
novel formalisation of artifact systems in the context of multi-agent systems
operating on them. Differently from the usual process-based models of services,
the semantics we give explicitly accounts for the data structures on which
artifact systems are defined. We study the model checking problem for
artifact-centric multi-agent systems against specifications written in a
quantified version of temporal-epistemic logic expressing the knowledge of the
agents in the exchange. We begin by noting that the problem is undecidable in
general. We then identify two noteworthy restrictions, one syntactical and one
semantical, that enable us to find bisimilar finite abstractions and therefore
reduce the model checking problem to the instance on finite models. Under these
assumptions we show that the model checking problem for these systems is
EXPSPACE-complete. We then introduce artifact-centric programs, compact and
declarative representations of the programs governing both the artifact system
and the agents. We show that, while these in principle generate infinite-state
systems, under natural conditions their verification problem can be solved on
finite abstractions that can be effectively computed from the programs. Finally
we exemplify the theoretical results of the paper through a mainstream
procurement scenario from the artifact systems literature
MCMAS-SLK: A Model Checker for the Verification of Strategy Logic Specifications
We introduce MCMAS-SLK, a BDD-based model checker for the verification of
systems against specifications expressed in a novel, epistemic variant of
strategy logic. We give syntax and semantics of the specification language and
introduce a labelling algorithm for epistemic and strategy logic modalities. We
provide details of the checker which can also be used for synthesising agents'
strategies so that a specification is satisfied by the system. We evaluate the
efficiency of the implementation by discussing the results obtained for the
dining cryptographers protocol and a variant of the cake-cutting problem
Reasoning about Knowledge and Strategies under Hierarchical Information
Two distinct semantics have been considered for knowledge in the context of
strategic reasoning, depending on whether players know each other's strategy or
not. The problem of distributed synthesis for epistemic temporal specifications
is known to be undecidable for the latter semantics, already on systems with
hierarchical information. However, for the other, uninformed semantics, the
problem is decidable on such systems. In this work we generalise this result by
introducing an epistemic extension of Strategy Logic with imperfect
information. The semantics of knowledge operators is uninformed, and captures
agents that can change observation power when they change strategies. We solve
the model-checking problem on a class of "hierarchical instances", which
provides a solution to a vast class of strategic problems with epistemic
temporal specifications on hierarchical systems, such as distributed synthesis
or rational synthesis
Model checking GSM-based multi-agent systems
Business artifacts are a growing topic in service oriented computing. Artifact systems include both data and process descriptions at interface level thereby providing more sophisticated and powerful service inter-operation capabilities. The Guard-Stage-Milestone (GSM) language provides a novel framework for specifying artifact systems that features declarative descriptions of the intended behaviour without requiring an explicit specification of the control flow. While much of the research is focused on the design, deployment and maintenance of GSM programs, the verification of this formalism has received less attention. This thesis aims to contribute to the topic.
We put forward a holistic methodology for the practical verification of GSM-based multi-agent systems via model checking. The formal verification faces several challenges: the declarative nature of GSM programs; the mechanisms for data hiding and access control; and the infinite state spaces inherent in the underlying data. We address them in stages.
First, we develop a symbolic representation of GSM programs, which makes them amenable to model checking. We then extend GSM to multi-agent systems and map it into a variant of artifact-centric multi-agent systems (AC-MAS), a paradigm based on interpreted systems. This allows us to reason about the knowledge the agents have about the artifact system. Lastly, we investigate predicate abstraction as a key technique to overcome the difficulty of verifying infinite state spaces. We present a technique that lifts 3-valued abstraction to epistemic logic and makes GSM programs amenable to model checking against specifications written in a quantified version of temporal-epistemic logic.
The theory serves as a basis for developing a symbolic model checker that implements SMT-based, 3-valued abstraction for GSM-based multi-agent systems. The feasibility of the implementation is demonstrated by verifying GSM programs for concrete applications from the service community.Open Acces
A counter abstraction technique for the verification of robot swarms.
We study parameterised verification of robot swarms against temporal-epistemic specifications. We relax some of the significant restrictions assumed in the literature and present a counter abstraction approach that enable us to verify a potentially much smaller abstract model when checking a formula on a swarm of any size. We present an implementation and discuss experimental results obtained for the alpha algorithm for robot swarms
Verifying Security Properties in Unbounded Multiagent Systems
We study the problem of analysing the security for an unbounded number of concurrent sessions of a cryptographic protocol. Our formal model accounts for an arbitrary number of agents involved in a protocol-exchange which is subverted by a Dolev-Yao attacker. We define the parameterised model checking problem with respect to security requirements expressed in temporal-epistemic logics. We formulate sufficient conditions for solving this problem, by analysing several finite models of the system. We primarily explore authentication and key-establishment as part of a larger class of protocols and security requirements amenable to our methodology. We introduce a tool implementing the technique, and we validate it by verifying the NSPK and ASRPC protocols
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