SQL4X, a powerful language for simultaneously querying both relational and XML databases is presented. Using SQL4X, one can create both relations and XML documents as query results. Thus, SQL4X can be thought of as an integration language. In order to allow easy integration of XML documents with varied structures, SQL4X uses flexible semantics when querying XML. SQL4X is also a powerful query language. It can express quantification, negation, aggregation, grouping and path expressions. Datalog4x and Tree-Datalog4x, extensions of Datalog, are defined as elegant abstract models for SQL4X queries. Query containment is characterized for many common classes of SQL4X queries. Specifically, for Datalog4x queries, a complete characterization of containment of conjunctive queries and of unions of queries is presented. Equivalence of Datalog4x queries under bag-set semantics is also characterized. A sufficient condition for containment of Tree-Datalog4x queries is presented. This condition is shown to be complete for a large class of common queries.
|Original language||American English|
|Title of host publication||Database Programming Languages - 8th International Workshop, DBPL 2001, Revised Papers|
|Editors||Giorgio Ghelli, Gosta Grahne|
|Number of pages||18|
|State||Published - 2002|
|Event||8th International Workshop on Database Programming Languages, DBPL 2001 - Frascati, Italy|
Duration: 8 Sep 2001 → 10 Sep 2001
|Name||Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)|
|Conference||8th International Workshop on Database Programming Languages, DBPL 2001|
|Period||8/09/01 → 10/09/01|
Bibliographical notePublisher Copyright:
© Springer-Verlag Berlin Heidelberg 2002.