An agent-based architecture of an active Digital Library (DL) is first described, to illustrate how electronic service provision can be supported through the use of agents. The use of mobile agents is presented as a key enabler for allowing services to be combined from a variety of providers, each of which provide a subset of the total required service. Load balancing approaches are then used to illustrate how particular performance criteria can be achieved in service provision. Extrapolation of the approach to the general Service-Oriented computing model is also discussed. A DL composed of multi-spectral imagery of the Earth, as part of the Synthetic Aperture Radar Atlas (SARA) is then used to illustrate the concepts described. The load balancing technique proposed is based on a combination of the state and model-based approaches. Experimental results demonstrating the distribution of agent load among the servers that constitute the DL, and the optimization of performance provided by the adaptability of the model employed is presented. Such an approach is particularly suited to Grid environments, which can involve a composition of services from a variety of distributed data resources.
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