We present a framework for designing, in a declarative and flexible way, efficient migration programs and an undergoing implementation of a migration tool called RelOO whose targets are any ODBC compliant system on the relational side and the O_2 system on the object side. The framework consists of (i) a declarative language to specify database transformations from relations to objects, but also physical properties on the object database (clustering and sorting) and (ii) an algebra-based program rewriting technique which optimizes the migration processing time while taking into account physical properties and transaction decomposition. To achieve this, we introduce equivalences of a new kind that consider side-effects on the object database.
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