Mobile Agent Technology for the Management of Distributed Systems - a Case Study
Claudia Raibulet and Claudio Demartini, Politecnico di Torino, Italy
Mobile agent technology has become an alternative approach for the design of distributed systems to the traditional client-server and message-based architectures. The main difference between the two technologies is the key solution they provide for the distribution problems: local interaction and mobile logic versus location transparency. An important example of their application, where the advantages of mobile agent technology are exploited best, is the management of distributed systems.
The paper presents an implementation example of the mobile agents used to access and to manage information stored in the Distributed Database Repository (DDR), as specified within the ESPRIT Project "Network Oriented Application Harmonization". The DDR model represents a distributed information repository designed to ensure a common view of the system for any application. The immediate advantage of the DDR model is a unified perspective for several activities that concern the distributed resources of the industrial system (e.g., installation, maintenance and technical management).
Within the DDR model architecture, four distinct components are identified: DDR System Manager, DDR Database, DDR Plant Manager, and Management Information Base (MIBs). The DDR System Manager contains general information related to the whole distributed system, such as a complete directory of the system resources or the network wide topology information. In the DDR Database are stored information regarding only a local plant, such as a list of the devices connected to that plant or general data that provides the base features of the devices. Every device has associated a local MIB that contains all its detailed information.
The System Manager receives the user's requests. According to the scope of the request, it creates an agent to execute the query, an agent that will be sent to one or more DDR Plant Managers. The Plant Manager interrogates first the DDR Database and only if the information stored here is not enough to perform the query it will interrogate also the MIBs. The result is then sent to the System Manager.
As support for the mobile agents' implementation, the Voyager platform, developed by the ObjectSpace, Inc has been chosen. The DDR has been implemented as an object-oriented database in the Java environment.
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