Maintaining caching consistency for heterogeneous database systems

The fact of the increasingly globalized economy has driven many corporations to expand their business beyond their traditional database access. They want to access heterogeneous data source by a uniform query interface. One of the ways to view these systems is to postulate a global schema that provides a unifying data model for all the data sources. A query processor is in charge of reformulating queries written in terms of this global schema to queries on the appropriate source and integrating the answers into a global answer. To reduce the cost of response time and improve the performance, in generally, the integration system employ a cache technique which holds results of previous queries and results. however, a stale copy may return to users if the original has been modified and there is not any mechanism to notify the cached copy relative to the original stored on data sources. In this, paper, we intend to explore existing caching mechanisms to that give a solution to the issue of caching consistency in the integration systems.