Keyphrases
- expressive power
- query language
- relational algebra
- data model
- sparql queries
- data complexity
- first order logic
- transitive closure
- computational properties
- rdf data
- database
- constraint databases
- semantic web
- xml data
- query evaluation
- relation algebra
- relational calculus
- constraint query languages
- conjunctive queries
- regular expressions
- database systems
- databases
- complex objects
- association rules
- recursive queries