A heterogeneous distributed database system based on extended relational model

The most important requirement for a heterogeneous distributed database system (HDDBS) is the capability of providing an integrated view of its component databases that is transparent in data distribution and the heterogeneity of the components. While a HDDBS provides the logical integration of its constituent databases, it should preserve their autonomy. The authors propose a heterogeneous database management system which extends the relational model to integrate and capture the semantic heterogeneity of the component databases