Building Parameterized Canonical Representations to Achieve Interoperability among Heterogeneous Databases

This paper describes a technique to support interoperable query processing when multiple heterogeneous databases are accessed. We focus on the problem of supporting query transformation transparently , so a user can pose queries locally, without any need of global knowledge about diierent data models and schemas. To support interoperable query transformation, we need to resolve the connicts (i.e., represen-tational heterogeneities) for diierent databases. The connicts exist because semantically equivalent concepts may be deened in diierent ways in each model/schema. Further, we also need to consider the connicts due to the diierent query language utilized by each database. We propose two kinds of parameterized canonical representations, as a means of classifying and resolving heterogeneities. The rst canonical representation resolves heterogeneity based on query languages. The second canonical form resolves representational het-erogeneity based on using two diierent schemas/data models. This paper will focus on the second canonical representation. We rst enumerate the representational heterogeneities, and then explain how we can use the canonical representation to resolve these connicts. We brieey describe an algorithm for building the canonical knowledge base, and also an architecture for supporting interoperability. A query transformation mechanism will operate on the local query and the canonical knowledge base to generate an appropriate query for a remote database.