We have developed a multidatabase query system, OPM*QS, in the framework of the Object-Protocol Model (OPM). OPM*QS supports ad hoc queries over multiple heterogeneous databases via existing or retrofitted OPM interfaces. The current (first) version of OPM*QS has been developed between October 1995 and January 1996. This version of OPM*QS supports the expression of queries that combine (join) and manipulate data from multiple databases, where a database directory contains information on the OPM views (schemas) and remote access facilities of these databases. OPM*QS has been applied to queries over GSDB 2.0 and GDB 6.0.
The main purpose of the first version of OPM*QS was to demonstrate the feasibility of an OPM-based multidatabase approach to the problem of federating heterogenous molecular biology databases (MBDs). This version of OPM*QS also allowed us to gain experience in the area of constructing OPM-based multidatabase systems and of processing multidatabase queries. Some of this experience as well as our plans are discussed below.