Data synchronization for integration systems based on message digest

integration systems provide a unified, called global schema, to the user over various heterogeneous data sources. Users issue their queries against the global schema, and the system computes answers to queries by suitably accessing the sources. In order to speed up query, in generally, an integration system caches recent query results at the mediator. If a cache hit, the mediator returns required data directly to users without posing sub-queries to appropriate wrappers residing at data sources for extracting local results. Although cache can reduce the load on the integration system significantly, network congestion, and the latency of each request, it brings a question of cache consistency. That is, a stale cache might be returned to a client. Aimed at this question, in this paper; we propose a data consistency algorithm based on message digest.