Interoperable Query Processing From Object to Relational Schemas Based on a Parameterized Canonical Representation

Abstract

In this paper, we develop techniques for interoperable query processing between object and relational schemas. The objective is to pose a query against a local object schema and be able to share information transparently from target relational databases. Our approach is a mapping approach (as opposed to a global schema approach) and is based on using canonical representations (CR). We use one CR for resolving heterogeneity based on the object and relational query languages. We use a second parameterized CR to resolve representational heterogeneity between object and relational schema, and to build a mapping knowledge dictionary. There is also a set of mapping rules, based on the parameters of the CR, which defines the appropriate mapping between schemas. A query posed against the local object schema is first represented in the CR for queries, and then transformed by the mapping rules, to an appropriate query for the target relational schema, using relevant information from the mapping knowledge dictionary. The use of the parameterized CR allows us to build the mapping knowledge dictionary easily, and allows reusability of the mapping rules.

Scaling access to heterogeneous data sources with DISCO

“…Alternately, the capability of a mediator to resolve conicts is supported by the use of higher-order query languages or meta-models 22 32]. Here, too, the emphasis is on resolving con icts among schema and data models, to support interoperability of the queries.…”

“…In 32], some syntactic translation is required if all wrappers support the same functionality (with di erent syntax). However, since the same functionality i s a vailable in all data sources, the wrappers are not very complicated and the required syntactic translation is straightforward.…”

Scaling heterogeneous databases and the design of Disco

“…Mediators are also implemented by mapping knowledge bases that capture the knowledge required to resolve conflicts 'among the local schema, and transformation algorithms that support query mediation and interoperation among relational ,and object &mibases [7,19,26,27,28]. Here, too, scalability is a problem, since the higher-order queries or the mapping knowledge has to adapt, as additional sources are incorporated.…”