ach year more applications shift from intranets to the Internet, and Internet-oriented applications become more popular. To fully harness the Web's advantages, we must develop new design and programming paradigms. Traditional distributed applications assign a set of processes to a given execution environment that, acting as local-resource managers, cooperate in a network-unaware fashion. In contrast, the mobile-agent paradigm defines applications as consisting of network-aware entities-agents-which can exhibit mobility by actively changing their execution environment, transferring themselves during execution. 1 Thus, mobile agents offer several advantages over traditional approaches to Internet applications. They can • save significant bandwidth by moving locally to the resources they need; • carry the code to manage remote resources and do not need the remote availability of a specific server; • proceed without continuous network connections, because interacting entities can be moved to the same site when connections are available, and can then interact without requiring further network connections; and • work with mobile computing systems. Although mobile agents have recently attracted widespread interest, several development obstacles remain. The technology still lacks secure and efficient execution support, standardization, appropriate programming languages, and coordination models. Coordination-both between agents and between other entities that agents can encounter during execution in the hosting environments-plays a fundamental role in mobile-agent applications. We propose a taxonomy of possible coordination models for mobile-agent applications, then use our taxonomy to survey and analyze recent mobile-agent coordination proposals. Our case study, which focuses on a Web-based information-retrieval application, helps show that the mobility of application components and the distribution area's breadth imply coordination problems different from those concerning traditional distributed applications. In particular, we evaluate which coordination models have the necessary characteristics to suit both mobility and the Internet scenario. Suitable models include coordination paradigms based on fully uncoupling the interacting entities, such as Linda, 3,4 possibly enhanced with the ability to program specific reactions in response to interaction events. 5 Adopting such models can lead to simpler application designs than those derived from traditional coordination models. Our case study involves an information retrieval application. We start with the assumptions that HTML pages spread over the Internet store information and that a given user wants to find all HTML pages that include one specific keyword. The user knows one site-the search's starting point-at which can be found documents that match the keyword. The Internet applications face challenges that mobile agents and the adoption of enhanced coordination models may overcome. To win the race, coordination models have to be inspired by the Linda coordination model and enriched by programmable reactivity.
Presently, mobile agent Coordination can be divided into four models REF .
Mobile-agent coordination models for Internet applications
IEEE Computer
IEEE Computer
Computer Science