Design and implementation of a CORBA query service accessing EXPRESS-based data

We describe the design and implementation of a CORBA query service targeted to access data that is defined by the EXPRESS data modeling language. EXPRESS is used primarily in engineering domains (like CAD/CAM and GIS) to describe mostly product model data (like parts explosion or product geometry). In order to bring query facilities for EXPRESS-based data to CORBA a number of design decisions have to be taken, although the CORBA query service is standardized by the OMG. Among the most important and performance-indicating decisions are the definition of an appropriate query language and the description of the query result data structures. We discuss solutions to these topics and report on the experiences gained in designing and implementing our first CORBA query service for EXPRESS-based data.