A Simple Query Facility for the Objectivity/DB Persistent Object Manager

The query facility, which will be called OQL’ in the following, satisfies a practical need. The Objectivity/DB Persistent Object Manager, which is used at CERN in several projects for its low-overhead support of object persistency, provides as its sole way to dynamically query data without writing a specialized application program a facility called SQL++. The query language of this facility has several restrictions which make it unsuited for mining practical object-oriented databases. Among other things, it does not allow to follow associations and does not provide access to arrays/aggregations of values. Furthermore, as of release 5.0 of the Objectivity suite of products, it is not very reliable and often leads to critical application errors when complex database schemata are accessed which contain many of the unsupported design elements.