A PEER DATA SHARING SYSTEM COMBINING SCHEMA AND DATA LEVEL MAPPINGS

摘要

Peer data sharing systems use either schema-level or data-level mappings to resolve schema as well as data heterogeneity among data sources (peers). Schema-level mappings create structural relationships among different schemas. On the other hand, data-level mappings associate data values in two different sources. These two kinds of mappings are complementary to each other. However, existing peer database systems have been based solely on either one of these mappings. We believe that if both mappings are addressed simultaneously in a single framework, the resulting approach will enhance data sharing in a way such that we can overcome the limitations of the non-combined approaches. In this paper, we present a model of a peer database management system which allows a bi-level mapping that combines schema-level and data-level mappings into a single relational framework.We present the syntax and semantics of this new kind of mappings. Furthermore, we present an algorithm for query translation that uses the bi-level mappings. Our algorithm relies on tableau for expressing both queries and mappings.