Understanding schemas

Before the problem of schema integration and translation can be adequately addressed, a precise understanding of schemas is needed. The authors present an analysis of the notion of schema as used by existing integration methodologies. They show how inherent ambiguities and imprecision in traditional definitions of schema can hamper the development of formal schema integration methodologies. Specifically, traditional notion of schema contain data in the form of metadata, as well as superfluous structuring information that is not semantically meaningful. It is important to cleanly separate structural information from data, and remove from consideration artifacts of a specific data model or design methodology. To this end, they introduce the notion of a schema intension to capture the semantic content of a schema