Keyphrases
- expressive power
- query language
- relational algebra
- data complexity
- transitive closure
- data model
- first order logic
- query evaluation
- object oriented
- recursive queries
- database
- relational calculus
- complex objects
- aggregate functions
- computational properties
- constraint databases
- constraint query languages
- database query languages
- relational query languages
- conjunctive queries
- xml data
- relation algebra
- database systems