Epaminondas Kapetanios David Baer Björn Glaus Paul Groenewoud MDDQL-Stat: Data Querying and Analysis through Integration of Intentional and Extensional Semantics. 353-356 2004 conf/ssdbm/2004 SSDBM http://doi.ieeecomputersociety.org/10.1109/SSDBM.2004.49 db/conf/ssdbm/ssdbm2004.html#KapetaniosBGG04