Automatic Verification of Communicative Commitments using Reduction

In spite of the fact that modeling and verification of the Multi-Agent Systems (MASs) have been since long under study, there are several related challenges that should still be addressed. In effect, several frameworks have been established for modeling and verifying the MASs with regard to communicative commitments. A bulky volume of research has been conducted for defining semantics of these systems. Though, formal verification of these systems is still unresolved research problem. Within this context, this paper presents the CTLcom that reforms the CTLC, i.e., the temporal logic of the commitments, so as to enable reasoning about the commitments and fulfillment.  Moreover, the paper introduces a fully-automated method for verification of the logic by means of trimming down the problem of a model that checks the CTLcom to a problem of a model that checks the GCTL*, which is a generalized version of the CTL* with action formulae. By so doing, we take advantage of the CWB-NC automata-based model checker as a tool for verification. Lastly, this paper presents a case study drawn from the business field, that is, the NetBill protocol, illustrates its implementation, and discusses the associated experimental results in order to illustrate the efficiency and effectiveness of the suggested technique.   Keywords: Multi-Agent Systems, Model Checking, Communicative commitment's, Reduction

Typing Multi-Agent Systems via Commitments

Abstract. This work presents an agent typing system, that differently than most of other proposals relies on notions that are typical of agent systems instead of relying on a functional approach. Specifically, we use commitments to define types. The proposed typing includes a notion of compatibility, based on subtyping, which allows for the safe substitution of agents to roles along an interaction that is ruled by a commitment-based protocol. Type checking can be done dynamically when an agent enacts a role. The proposal is implemented in the 2COMM framework and exploits Java annotations. 2COMM is based on the Agent & Artifact meta-model, exploit JADE and CArtAgO, by using CArtAgO artifacts in order to reify commitment protocols

Specifying and verifying communities of Web services using argumentative agents

This thesis includes two main contributions: the first one is specifying the use of argumentative agents in the design and development of communities of Web services; the second is using a formal technique to verify communication protocols against given properties for these communities. Web services that provide a similar functionality are gathered into a single community, independently of their origins, locations, and ways of doing. Associating Web services with argumentative agents that are able to persuade and negotiate with others organizes these Web services in a better way so that they can achieve the goals they set in an efficient way. A community is led by a master component, which is responsible among others for attracting new Web services to the community, retaining existing Web services in the community, and identifying the Web services in the community that will participate in composite scenarios. Besides FIPA-ACL, argumentative dialogue games are also used for agent interaction. In this thesis, we use tableau-based model checking algorithm to verify our argumentative agent-base community of Web services negotiation protocol. This algorithm aims at verifying systems designed as a set of autonomous interacting agents. We provide the soundness, completeness, termination and complexity results. We also simulate our specification with Jadex BDI programming language and implement our verification with a modified and enhanced version of CWB-NC model checker. Keywords. Multi-agent systems, BDI agent architecture, model checking, agent oriented programming, FIPA-ACL, dialogue game, agent-based negotiation protocol, Jadex, CWB-NC

Analyzing the Interaction between Knowledge and Social Commitments in Multi-Agent Systems

Both knowledge and social commitments in Multi-Agent Systems (MASs) have long been under research independently, especially for agent communication. Plenty of work has been carried out to define their semantics. However, in concrete applications such as business settings and web-based applications, agents should reason about their knowledge and their social commitments at the same time, particularly when they are engaged in conversations. In fact, studying the interaction between knowledge and social commitments is still in its beginnings. Therefore, in this thesis, we aim to provide a practical and formal framework that analyzes the interaction between knowledge and communicative social commitments in MASs from the semantics, model checking, complexity, soundness and completeness perspectives. To investigate such an interaction, we, first, combine CTLK (an extension of computation Tree Logic (CTL) with modality for reasoning about knowledge) and CTLC (an extension of CTL with modalities for reasoning about commitments and their fulfillments) in one new logic named CTLKC. By so doing, we identify some paradoxes in the new logic showing that simply combining current versions of commitment and knowledge logics results in a language of logic that violates some fundamental intuitions. Consequently, we propose CTLKC+, a new consistent logic of knowledge and commitments that fixes the identified paradoxes and allows us to reason about social commitments and knowledge simultaneously in a consistent manner. Second, we use correspondence theory for modal logics to prove the soundness and completeness of CTLKC+. To do so, we develop a set of reasoning postulates in CTLKC+ and correspond them to certain classes of frames. The existence of such correspondence allows us to prove that the logic generated by any subset of these postulates is sound and complete, with respect to the models that are based on the corresponding frames. Third, we address the problem of model checking CTLKC+ by transforming it to the problem of model checking GCTL∗ (a generalized version of Extended Computation Tree Logic (CTL∗) with action formulas) and ARCTL (the combination of CTL with action formulas) in order to respectively use the CWB-NC automata-based model checker and the extended NuSMV symbolic model checker. Moreover, we prove that the transformation techniques are sound. Fourth, we analyze the complexity of the proposed model checking techniques. The results of this analysis reveal that the complexity of our transformation procedures is PSPACE-complete for local concurrent programs with respect to the size of these programs and the length of the formula being checked. From the time perspective, we prove that the complexity of the proposed approaches is P-complete with regard to the size of the model and length of the formula. Finally, we implement our model checking approaches and report some experimental results by verifying the well-known NetBell payment protocol against some desirable properties

Probabilistic and Epistemic Model Checking for Multi-Agent Systems

Model checking is a formal technique widely used to verify security and communication protocols in epistemic multi-agent systems against given properties. Qualitative properties such as safety and liveliness have been widely analysed in the literature. However, systems also have quantitative and uncertain (i.e., probabilistic) properties such as degree of reliability and reachability, which still need further attention from the model checking perspective. In this dissertation, we analyse such properties and present a new method for probabilistic model checking of epistemic multi-agent systems specified by a new probabilistic-epistemic logic PCTLK. We model multiagent systems distributed knowledge bases using probabilistic interpreted systems. We also define transformations from those interpreted systems into discrete-time Markov chains and from PCTLK formulae to PCTL formulae, an existing extension of CTL with probabilities. By so doing, we are able to convert the PCTLK model checking problem into the PCTL one. We address the problem of verifying probabilistic properties and epistemic properties in concurrent probabilistic systems as well. We then prove that model checking a formula of PCTLK in concurrent probabilistic systems is PSPACE-complete. Furthermore, we represent models associated with PCTLK logic symbolically with Multi-Terminal Binary Decision Diagrams (MTBDDs). Finally, we make use of PRISM, the model checker of PCTL without adding new computation cost. Dining cryptographers protocol is implemented to show the applicability of the proposed technique along with performance analysis and comparison in terms of execution time and state space scalability with MCK, an existing epistemic-probabilistic model checker, and MCMAS, a model checker for multi-agent systems. Another example, NetBill protocol, is also implemented with PRISM to verify probabilistic epistemic properties and to evaluate the complexity of this verification