OQL = ObjectQueryLanguage = a query language for ObjectOrientedDatabase''''s.
It's the Object database equivalent of StructuredQueryLanguage (SQL).

See [ISBN: 1558604634] "The Object Database Standard," ODMG 2.0, R.G.G. Cattell (ed.), Morgan Kaufmann, 1997.

Examples:
* http://www.odmg.org/ - ODMG - "Object Data Management Group; The Standard for Storing Objects" - [includes Antlr grammar for OQL/ObjectQueryLanguage]
* http://www.db.ucsd.edu/cse132B/oql.htm - tutorial for O2
* http://www.chimu.com/projects/form/learningForm/index_6.html - "OQL: FORM?s Object Query Language"
* http://docs.codehaus.org/display/PREVAYLER/Object+Query+Languages - ad-hoc "querying" options for an in-memory database. (See ThePrevayler)

Slide Presentations:
* http://www.cse.ohio-state.edu/~doug/CSE671/Transparencies/oql.pdf - reasonably good slide presentation (in 6-up printable form)
* http://lbdwww.epfl.ch/e/teaching/SlidesBDA/BDAOQL.pdf
* http://www.mm.di.uoa.gr/~toobis/seminar/OQL/index.htm - a brief slide presentation

Related:
* http://www.nicve.salford.ac.uk/~norman/kaleidoquery.pdf - "Kaleidoquery: A Visual Query Language for Object Databases"