Conceptual models of heterogeneous data representation

Lately in the industry of an information technology the question on integration of heterogeneous sources of the data is even more often brought up. In difference to homogeneous systems, heterogeneous data source systems can be described by various data models. Integration of heterogeneous data source means creation of the general scheme of the description of the given all subsystems for the unified access to the data, with preservation of semantics of this data. Our article is attempt of consideration of the various models used to describe the general scheme of databases.