A Discovery Service for Very Large, Dynamic Grids

Discovery of service providers that are useful to service requesters is a common problem in service oriented systems, such as grids and ever more the whole World Wide Web itself. Current solutions do not address this problem adequately in very large, highly dynamic systems. Being usually designed for systems with predominantly static and relatively small set of information on existing service providers, they can not cope with large numbers of advertised services, service providers arbitrarily joining and leaving the system, and the constantly changing properties of the advertised services. This paper presents an architecture and a proof-ofconcept implementation of a discovery service for large, highly dynamic service oriented systems, based on the peerto- peer paradigm. Our discovery service on one hand allows for dynamic publication of service advertisements by very large numbers of service providers that arbitrarily join and leave the system. On the other hand it provides means for service requesters to dependably discover service providers that fullfil complex conditions specified by the requester. Also, the system allows the requester to dynamically establish a contract with the discovered service provider that describes the conditions under which the service will be provided to the requester.