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RCACM Role-based Context-awareness Coordination Model for Mobile Agent Applications 1


RCACM: Role-based Context-awareness Coordination Model for Mobile Agent Applications1
Xinhuai Tang, Yaying Zhang, Jinyuan You Department of Computer Science and Engineering, Shanghai Jiao Tong University, Shanghai 200030, P.R.China {tang-xh, zhang-yy, you-jy }@cs,sjtu.edu.cn

Abstract. In this paper, we present an RCACM coordination model for mobile computing applications based on mobile agents. The key idea in RCACM is the role-based context-awareness hierarchical coordination model. In this model, local programmable reactive tuple space is introduced to address the contextaware coordination problems and hierarchical distributed tuples can make agents dynamically acquire information about resource location and availability according to their permissions; role mechanism is adopted for access control to prevent unauthorized access.

1 Introduction
In mobile computing systems, an application may be composed of several mobile agents that cooperatively perform a task[1]. Multiple mobile agents are in need of coordinating their activities with each other, and also accessing resources on hosting execution environments. Furthermore, when an agent transfers to a new environment, the interaction information it accesses and the outside world it perceived might have changed. For an agent, its execution result on one site may be different from the execution result on other site because of the different execution environment. So the migration of mobile agent introduced context-aware coordination issues [2]. Generally, coordination technologies concern with enabling interaction among agents and help them cooperate with each other [3]. However access control should also be considered to constrain interaction to ensure data privacy and integrity, especially when agent mobility is introduced. At present the combination of coordination and access control remains an open problem in the design and implementation of mobile agent applications. This paper aims to present a role-based context-aware coordination model(RCACM) in mobile agent applications. We focus on context-awareness secure coordination, that is, the coordination of activities with context awareness due to agent mobility and with insurance of data integrity.

1

This paper is supported by the Shanghai Science and Technology Development Foundation under Grant No. 03DZ15027 .

2 Role-based context-aware coordination
2.1 Overview In order to overcome weakness and still making use of advantages Linda tuple space has, we rebuild the tuple space from passive data storage to reactive programmable coordination media, which can embody computing capabilities within the tuple space. As a consequence, the role-based context-aware coordination model(RCACM) in mobile agent applications is proposed, which extends classical Linda model. There is no global tuple space in the mobile agent system. Instead, multiple distributed tuple spaces are used for agent coordination. The model transfers the global coupling interactions to local uncoupling interactions. Agent interactions take place on the local execution environment on the destination site of migrating agent. Local space can be accessed in an asynchronous and anonymous way as in Linda. Therefore, interaction tuple space can act as a gateway for agent to access resources in the network. RCACM supports a coordination paradigm where agents can migrate from one computing environment to another to interact with each other. The architecture of role-based context dependent coordination is as in Fig.1.

Agent App1

AgentApp2

Agent App1

Agent App2

role checking reactive tuple space
enviroment1 policy App1& App2 policy

role checking reactive tuple space
enviroment2 policy App1& App2 policy

site 1

site 2

Fig. 1. Architecture of role-based context-awareness coordination

In RCACM, withoutglobal shared tuple space, multiple tuple spaces are distributed over the network to assist the coordination task. Reactive programmable tuple space is responsible for handling coordination activities, including environment-aware and application-aware coordination. 2.2 Role mechanism and Reactions in tuple space Coordination and access control are two strictly related topics in open distributed applications. One can easily imagine malicious agents attempting to access private

information or modify private data. So a server receiving interaction of external agent needs to impose some requirements to ensure no violation to security concerns of host server. Similarly, the external agent also needs to ensure that its execution at the host server site will not lose its integrity or security. A role can be defined as the behavior and the set of the capabilities expected for the agent that plays such roles. An agent might hold multiple roles. Every role has its corresponding capabilities. We use {read, take, write, execution, new,…} to indicate the set of agent operation abilities. Every element indicates the capability to execute the corresponding operation. Assigning roles to an agent means to associate with it capabilities that describes all the operations the agent intends to perform, while ignoring the specific location it will execute on. In RCACM, tuple space is programmable and reactive. Site manager at every site in the mobile agent system can implement and enforce application specific and local environment specific policies by programming the behaviors of tuple space. Operation behaviors can be associated with specific events.

2.3 Environment-aware and application-aware coordination In mobile agent applications, there are always both agent related application specific policy and environment specific policy. When a site in the network opens itself to external agents for execution, it must prevent malicious agents from damaging its data and resource. On the other side, when an agent migrates to a new site, it cannot predict the policy of the site[4]. If mobile agent needs to handle all unexpected policy related problems, this would certainly make it even more complex and make the system difficult to be scalable. So with programmable reactive tuple space, environment-awareness policies such as security policies can be integrated into the behavior of tuple space. Mobile agents can be under restrictions on the new site transparently. In RCACM, when an agent arrives at a site, it is bound to the tuple space on the destination site and can use it to coordinate itself with other agents and to access local resources. The local tuple space is implemented as Java objects. Every tuple is implemented as a Java object. To define the environment infrastructure, an administrator has to choose the roles the environment supports and define the application and environment policies to coordinate activities via the tuple space.

3 Conclusion
Mobile agent system demonstrated great potential in designing and implementing complex distributed and concurrent software systems. It has involved in many

applications such as e-commerce, remote information retrieval, remote diagnostic clinic and military war simulation. We propose a role-based context-awareness coordination model, which is suitable for interactions between agents and between agents and environment in mobile agent systems. The model consists of three parts. (1) A role mechanism is presented for security concerns; (2) Global coupling interaction space has been changed to locally uncoupling interaction space to facilitate information access for mobile agents; (3) Programmable reactive tuple space is used to solve the problem introduced by context-awareness coordination. Environment-awareness and applicationawareness coordination policies can be integrated into the tuple space.

References
1. Gian Pietro Picco, Mobile Agents: An Introduction, Journal of Microprocessors and Microsystems, 25(2)(2001) 65-74. 2. Giacomo Cabri, Letizia Leonardi, Engineering Mobile Agent Applications via Contextdependent Coordination. IEEE transaction on software engineering 28(11) (2002) 10401056. 3.M. Cremonini, A. Omicini, F. Zambonelli, Coordination and Access Control in Open Distributed Agent Systems: The TuCSoN Approach, Proceedings of 4th International Conference on Coordination Languages and Model(COORDINATION 2000), LNCS 1906, Springer, Limassol, Cyprus, 2000, pp. 99-114. 4. Davide Rossi, Giacomo Cabri, Enrico Denti, Tuple-based technologies for coordination, In A. Omicini, F.Zambonelli, M. Klusch, R. Toldsdorf(Eds.), Coordination of Internet Agents, Springer, (2001)83-109


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