Joos Heintz Bart Kuijpers Constraint Databases, Data Structures and Efficient Query Evaluation. 1-24 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3074&spage=1 2004 conf/cdb/2004 CDB db/conf/cdb/cdb2004.html#HeintzK04