Abstract: Establishing schema mappings among different schemas is a key to solve the problem of schema heterogeneity in multidatabase systems Since an integrated data model suitable for the transformation is the basis of schema mappings, an XML based integrated data model （XIDM） is presented as the common data model to integrate multiple heterogeneous data sources such as database tables, files and web documents in a multidatabase system An XIDM based approach of schema mapping among global schemas, export schemas, and local schemas is also given Then, the illustration and implementation of global and local mappings in multidatabase prototype—Panorama system are shown, and finally, the performance evaluation and analysis of XIDM based schema mapping are also discussed