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The paper proposes a novel model checking-based approach towards verifying the compliance of intelligent agent-based web services with contracts regulating their compositions specified in the Business Process Execution Language (BPEL). Unlike the existing approaches in the literature, the main contribution and impact of the introduced approach is the ability to verify intelligent and autonomous composite web services by capturing and describing in details both compliance and violation behaviors, how the system can distinguish between them, and how the system reacts and can be recovered after each violation. The approach encompasses three contributing parts, namely: 1) the marking process of an extended BPEL; 2) the transformation of the extended and marked BPEL to an automata model; and 3) the encoding of the resulting automata model into the Interpreted Systems Programming Language (ISPL), the input language of the MCMAS model checker for intelligent and autonomous multi-agent systems. In the first part, we extend BPEL that specifies the business process of the composition by creating custom activities called labels. We use those labels as means to represent the specifications and mark the points the developer aims to verify. A significant advantage of this labeling is the ability to highlight specific points in the design to be verified and to distinguish compliance behaviors from violations, which makes this verification focused and highly efficient. In the second part, we introduce new transformation rules to transform the extended and marked BPEL to an automata model. This transformation requires a prior modeling of agent-based web services composition using automata definitions. In the third part, we introduce algorithmic translation rules encoding the resulting automata model into ISPL. This translation makes model checking the behavior of our contract-driven compositions possible. A novel characteristic of the proposed approach is the automatic generation of the properties against which the system is verified from the composition’s implementation, which is technically challenging. The verification properties are expressed in the Computation Tree Logic of Commitments (CTLC). Technically, CTLC provides a powerful representation to formally model 1) interactions among multi-agent based web services and 2) compliance and violation behaviors within composite business contracts by making use of communicative commitment operators. CTLC also includes a fulfillment operator which helps formally check the compliance with business contracts and specify the system recovery. A detailed case study from expert and intelligent systems domain along with experimental results are also reported in the paper. Finally, the main impact and significance of the paper on expert and intelligent systems is the ability to use these systems safely since there is a way to verify if the intelligent components behave according to and in compliance with the underlying regulating contracts. [ABSTRACT FROM AUTHOR]

Highlights: [•] We formalize the question of competing or cooperating for communities of agent-based services. [•] We use the game-theoretic best response technique to analyze competitive/cooperative behaviors of autonomous services within communities. [•] We analyze the computational complexity of the proposed decision mechanism and prove its efficiency. [•] We confirm the theoretical results through extensive simulation using real dataset of services on the web. [ABSTRACT FROM AUTHOR]

Abstract: In agent and (web) service computing, collaboration takes place when distributed entities have limited knowledge and capabilities, so they cannot perform required tasks without interacting and helping each other. For instance, web services, which are loosely-coupled business applications, are called to cooperate in distributed settings for the sake of efficiency. In this context, agents that abstract and act on behalf of web services could act in cooperative groups that gather a number of agents sharing some common goals. Enabling those agent-based web services to decide about their strategies in terms of joining and acting within groups, inviting other agents to join, and leaving a group to act alone is an open issue that we address in this work. In this paper, we propose a framework where agent-based web services select strategies that maximize their outcomes. These strategies could be categorized into cooperative strategies involving other agents and strategies that highlight the single operative attitude. Although cooperation seems to bring better utility to cooperative agents, we highlight that web services in some environments obtain better outcome while they act individually (i.e., outside the group). This means that the cost of cooperation (in some particular cases) might negatively influence the outcome and obtained utility. As solution, we propose in this paper (1) an agent-based model that formalizes web services decision making where different parameters are considered; and (2) a game-theoretic framework that analyzes the web services strategies allowing them to maximize their acting performance where non-zero-sum games are being used. The paper presents theoretical results, which are also confirmed through extensive simulations. [Copyright &y& Elsevier]

• We propose a formal approach to model, verify and test avionics systems. • We use intelligent agents to model the components of the landing gear system. • We introduce extended interpreted systems to reason about interactions and actions. • We introduce a testing methodology that follows a test-driven development approach. • We use MCMAS+ to generate traces for test suites achieving new coverage criteria. The paper contributes by introducing a novel, formal and operational approach that addresses the open challenging issues of modeling, verifying, and testing intelligent critical avionics systems. We advance the state-of-the-art by unifying the three challenges and considering the intelligence, autonomy, and accountability of the components as first citizen concepts. The proposed methodology is effectively applied to a real, practical and complex case study of intelligent avionics systems, namely the landing gear system and uses multi-agent systems to model each main component in the system as an intelligent agent. We also introduce the formalism of extended interpreted systems that supports intelligence, autonomy, communication, input and output actions, predicate conditions and post-conditions. The paper adopts the computation tree logic of conditional commitments to model communication among autonomous agents and trace its progress. The symbolic model checker of this logic is used to run the verification of the system model, encoded in an extended input language, against coverage criteria and properties. Furthermore, we introduce a new testing methodology that: 1) Follows a test-driven development approach; 2) performs unit testing, component testing, and system testing in each increment; and 3) uses model checking to generate automatically counterexamples and witness traces interpreted into concrete test suites that achieve new coverage criteria. The experimental results showed the efficiency and scalability of the developed approach against a transformation-based technique. Finally, the computational complexity of the developed approach is analysed. [ABSTRACT FROM AUTHOR]