Squirrel Phase 1 : Generating Data Integration

This paper presents a framework for data integration that is based on using \Squirrel integration mediators" that use materialization to support integrated views over multiple databases. These mediators generalize techniques from active databases to provide incremental propagation of updates to the materialized views. A framework based on \View Decomposition Plans" for optimizing the support of materialized integrated views is introduced. The paper describes the Squirrel prototype currently under development, which can generate Squirrel mediators based on high-level speciications. The integration of information by Squirrel-generated mediators is expressed primarily through an extended version of a standard query language, that can refer to data from multiple information sources. In addition to materializing an integrated view of data, these mediators can monitor conditions that span multiple sources. The Squirrel framework also provides eecient support for the problem of \object match-ing", that is, determining when object representations (e.g., OIDs) in diierent databases correspond to the same object-in-the-world, even if a universal key is not available. To establish a context for the research, the paper presents a taxonomy that surveys a broad variety of approaches to supporting and maintaining integrated views.