A query processing strategy for replication in heterogeneous databases

It is becoming increasingly important to manage preexisting autonomous databases as a repository resource. However, since the same entity in the real world may be modeled by different pre-existing databases, some data are replicated at different sites. In this research, we provide a new reference architecture for heterogeneous database systems. Based on this architecture, we propose a two-phase query processing strategy to determine the sites from which the query retrieves the replicated data. In the first phase, we use a pattern-based query processing technique to identify objects that satisfy the specified global query. Then in the second phase, we select the best sites to retrieve the data. Examples are used to illustrate the heuristic rules proposed in this paper