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An Architectural Description Language for Secure Multi-Agent Systems

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An Architectural Description Language for Secure Multi-Agent Systems An Architectural Description Language for Secure Multi-Agent Systems Haralambos Mouratidis1,a, Manuel Kolpb, Paolo Giorginic, Stephane Faulknerd aInnovative Informatics Group, School of Computing, IT and Engineering, University of East London, England b Information Systems Research Unit, Catholic University of Louvain (UCL), Belgium c Department. of Information and Communication Technology, University of Trento, Italy d Information Management Research Unit, University of Namur, Belgium Abstract. Multi-Agent Systems (MAS) architectures are gaining popularity for building open, distributed, and evolving information systems. Unfortunately, despite considerable work in the fields of software architecture and MAS during the last decade, few research efforts have aimed at defining languages for designing and formalising secure agent architectures. This paper proposes a novel Architectural Description Language (ADL) for describing Belief-Desire-Intention (BDI) secure MAS. We specify each element of our ADL using the Z specification language and we employ two example case studies: one to assist us in the description of the proposed language and help readers of the article to better understand the fundamentals of the language; and one to demonstrate its applicability. Keyword: Architectural Description Language, Multi-Agent Systems, Security, BDI Agent Model, Software Architecture 1 Corresponding Author: [email protected] 1 1. Introduction However, as the expectations of business stakeholders are changing day after day; and The characteristics and expectations of as the complexity of systems, information new application areas for the enterprise, and communication technologies and such as e-business, knowledge management, organisations is continually increasing in peer-to-peer computing, and web services, today’s dynamic environments; developers are deeply modifying information systems are expected to produce architectures that engineering. Most of the systems designed, must handle more difficult and intricate for this kind of application areas, are now de requirements than ever before. facto concurrent and distributed. They tend A critical issue in the design and to be open and dynamic, in that they exist in construction of any complex information a changing organizational and operational system is its architecture. That is, its gross environment where new components can be organization as a collection of interacting added, modified, or removed at any time. It components. A rigorous architectural design is also important that such systems are can ensure that a system will satisfy key secure, since they are often used for the requirements in such areas as performance, management and storage of sensitive reliability, portability, scalability, and information, such as medical, financial and interoperability [40]. To assist developers in private data. specifying information system architectures, Given these needs, many researchers are architectural description languages are used. looking for paradigms that will enable them An Architectural Description Language to conceptualize, design and implement (ADL) provides a concrete syntax for information systems that can operate specifying architectural abstractions in a effectively in such circumstances. In this descriptive notation. Architectural context, we advocate the use of Multi-Agent abstractions concern the structure of the Systems (MAS) to build today’s enterprise system’s components, their behaviour, and information systems. MAS architectures their interrelationships. appear to be more flexible, modular and Unfortunately, despite the progress on the robust than traditional; including object- field of software architectures (see for oriented ones. MAS do represent dynamic instance [2], [17], [28], [30], [39]) and the and evolving structures and components, simultaneous progress on MAS research; which can change at run-time to benefit few research efforts have aimed at truly from the capabilities of new system entities defining description languages for MAS or replace obsolete ones. Moreover, MAS architectures, and even these do not represent a suitable paradigm for the adequately include important issues of MAS consideration of security challenges such as security. This paper deals with this introduced by the current information problem and it proposes a novel ADL for systems. Security issues, within an agent MAS, which defines a “core” set of system context, will require for the agents of structural, behavioural and security the system to consider the security concepts, including relationships and requirements, when specifying their constraints, which are fundamental for a objectives and interactions, and therefore complete MAS ADL. The language, called cause the propagation of security requirements to the whole system [34]. 2 SKwyRL-ADL2, aims to describe secure world, which force the agent to act and Belief-Desire-Intention (BDI) MAS. react to change in quasi real-time The paper is structured as follows. Section fashion. Pro-activeness means that an 2 overviews the notions of agent and MASs agent’s behaviour is not exclusively and identifies the main concepts of the BDI reactive but it is also driven by internal model, which is used in our ADL. Section 3 goals, i.e. an agent may take initiative. discusses security in MAS and Section 4 With these concepts in mind, a MAS can models SKwyRL-ADL using the Z be defined as a set of autonomous and specification language. An example case proactive agents that interact with each other study is used to assist reader understanding to achieve common or private goals. This of the language’s elements. Section 5 definition leads us to two different types of demonstrates the applicability of the MAS: Cooperative or Competitive. proposed ADL with the aid of a real case A Cooperative MAS has a unique high- study from the e-media domain. Section 6 level global goal (or set of goals) describes related work; it indicates how that decomposed recursively into parallel work has influenced the presented work, and activities to be performed by the set of it discusses how the presented work differs agents that compose that MAS. This kind of from related work. The last section system is typically adapted to perform summarizes the contributions of the paper distributed problem solving. In a and discusses future work. Competitive MAS, each of the component agents has its own set of goals that may or may not meet those of other agents. In this 2. Agents and Multi-Agent Systems case the MAS is an architecture that allows agents to interact, while each one pursues An agent defines a system entity, situated personal goals and defends own interests. in some environment that is capable of This kind of system meets typical flexible autonomous action in order to meet engineering requirements of e-commerce, its design objectives [46]. Three key information retrieval applications, web concepts support this definition: services or peer-to-peer networks. In such • Situatedness: an agent receives input environments, every agent generally from the environment it operates and can represents either a client, aiming at perform actions, which change the obtaining some resources or have some environment in some way; service accomplished; or a provider, aiming • Autonomy: an agent is able to operate at selling resources or services at a certain without direct, continuous supervision. (not necessarily financial) cost. Each agent In other words it has full control over its pursues the goals of the (human or system) own actions; actor it represents, and these goals can • Flexibility: an agent is not only reactive usually be in conflict. but also pro-active. Reactivity means In order to reason about these goals and that an agent has perceptions of the act in an autonomous way, agents are usually built on rationale models and 2 reasoning strategies that have roots in Socio-Intentional ArChitecture for Knowledge various disciplines including Artificial Systems & Requirements ELicitation (www.isys.ucl.ac.be/ skwyrl) Intelligence, Cognitive Science, Psychology 3 or Philosophy. Agent models are executed one step at a time. A step can proliferating; some include learning query or change the beliefs; it can perform capabilities, others intelligent agendas based actions on the external world; and it can on statistics, others yet are based on genetic submit new goals. The operations performed algorithms and so on. An exhaustive by a step may generate new events that, in evaluation of these models is out of the turn, may start new plans. A plan succeeds scope of this paper or even this research when all its steps have been completed; it work. However, a simple yet powerful and fails when certain conditions are not met. mature model coming from Cognitive Science and Philosophy that has received a great deal of attention, notably in Artificial 3. MAS and Security Intelligence, is the Belief-Desire-Intention (BDI) model [6]. This approach has been Security of software systems, agent- intensively used to study the design oriented, object-oriented or otherwise, is rationale of agents and is proposed as a concerned with methods providing cost keystone model in numerous agent-oriented effective and operationally effective development environments such as JACK3 protection from undesirable events[30]. In or JADE4. The main concepts of the BDI principle security is usually defined in terms agent model are (except the notion of agent of the existence of any of the following itself that we have just
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