Keyphrases
- expressive power
- closure properties
- computational properties
- query language
- first order logic
- transitive closure
- data complexity
- relational algebra
- query answering
- grammatical inference
- description logics
- context free grammars
- databases
- natural language
- data exchange
- recursive queries
- constraint query languages
- database query languages
- decision procedures
- incomplete information
- artificial intelligence