Composing Schema Mappings: Second-Order Dependencies to the Rescue

A schema mapping is a specification that describes how data structured under one schema (the source schema) is to be transformed into data structured under a different schema (the target schema). Schema mappings play a key role in numerous areas of database systems, including database design, information integration, and model management. A fundamental problem in this context is composing schema mappings: given two successive schema mappings, derive a schema mapping between the source schema of the first and the target schema of the second that has the same effect as applying successively the two schema mappings. In this paper, we give a rigorous semantics to the composition of schema mappings and investigate the definability and computational complexity of the composition of two schema mappings. We first study the important case of schema mappings in which the specification is given by a finite set of source-totarget tuple-generating dependencies (source-to-target tgds). We show that...

• Type: Conference
• Year: 2004
• Where: PODS
• Authors: Ronald Fagin, Phokion G. Kolaitis, Lucian Popa, Wang Chiew Tan
• Keywords: Database, PODS 2004, Schema Mappings, Successive Schema Mappings, Target Schema