On Preservation under Homomorphisms and Unions of Conjunctive Queries.
Albert AtseriasAnuj DawarPhokion G. KolaitisPublished in: PODS (2004)
Keyphrases
- unions of conjunctive queries
- data exchange
- conjunctive queries
- query answering
- transitive closure
- decision procedures
- probabilistic databases
- answering queries
- relational queries
- data complexity
- relational algebra
- dl lite
- data management
- query containment
- query evaluation
- schema mappings
- data integration
- query language
- np complete
- integrity constraints
- special case
- regular path queries
- uncertain data
- expressive power
- first order logic
- query processing
- reasoning tasks
- theorem proving
- databases
- database queries
- sql queries
- database systems
- data mining