Factorised representations of query results: size bounds and readability

We introduce a representation system for relational data based on algebraic factorisation using distributivity of product over union and commutativity of product and union. We give two characterisations of conjunctive queries based on factorisations of their results whose nesting structure is defined by so-called factorisation trees. The first characterisation concerns sizes of factorised representations. For any query, we derive a size bound that is asymptotically tight within our class of factorisations. We also characterise the queries by tight bounds on the readability of the provenance of result tuples and define syntactically the class of queries with bounded readability. Categories and Subject Descriptors H.2.4 [Database Management]: Systems—Relational Databases, Query Processing General Terms Theory, Algorithm Design Keywords conjunctive queries, data factorisation, hierarchical queries, provenance, query evaluation, readability, size bounds

• Type: Journal
• Year: 2012
• Where: ICDT
• Authors: Dan Olteanu, Jakub Zavodny
• Keywords: Conjunctive Queries, Database, Database Management Systems, ICDT 2012, Size Bounds