Keyphrases
- query language
- mathematical theory
- data model
- expressive power
- object oriented
- database
- relational algebra
- digital libraries
- complex objects
- formal language
- query evaluation
- formal specification
- regular expressions
- formal methods
- real world
- transitive closure
- formal model
- query interface
- structured documents
- computational intelligence
- multimedia
- information retrieval
- machine learning
- mathematical modeling
- recursive queries
- algebraic operators