Integration of Inheritance Trees as Part of View Generation For Database Federations

Schema integration is the basis for successfully building a database federation. Current proposals directly integrate the different schemata using a semantical powerful data model, for example an extended ER model or an object-oriented model. We propose instead to use for integration a semantical poor model and build semantically rich representations as external views only. This approach enables a flexible integration and derivation especially for inheritance trees. We present an algorithm enabling the derivation of different inheritance trees as external views onto an integrated schema. The resulting inheritance tree can be influenced by giving priorities to input classes or attribute combinations and satisfies several formalized quality criteria for external views.