Relational completeness of query languages for annotated databases
Faculty of Sciences. Mathematics and Computer Science

article

2007
2007

Computer. Automation

Lecture notes in computer science

4797(2007)
, p. 127-137

0302-9743

E

English (eng)

Annotated relational databases can be queried either by simply making the annotations explicitly available along the ordinary data, or by adapting the standard query operators so that they have an implicit effect also on the annotations. We compare the expressive power of these two approaches. As a formal model for the implicit approach we propose the color algebra, an adaptation of the relational algebra to deal with the annotations. We show that the color algebra is relationally complete: it is equivalent to the relational algebra on the explicit annotations. Our result extends a similar completeness result established for the query algebra of the MONDRIAN annotation system, from unions of conjunctive queries to the full relational algebra.