Semantic interoperability of multitemporal relational databases

Interoperability is concerned with the interaction of databases of different kinds. In this paper we consider semantic interoperability between relational database systems of different temporal types (snapshot, transaction-time, valid-time or bitemporal), and between relations of different temporal types within the same system. The temporal natural join is the most important operation for combining data stored in different relations and, thus, is also mainly concerned in temporal interoperability problems. Therefore, a suitable variant of algorithms for temporal natural join is presented. The variant is based on the translation of temporally heterogeneous relations into a common format and on a mechanism of completion of relations which store incomplete information along some time dimension. Semantic and operative issues connected with the proposal are discussed.