Keyphrases
- relational databases
- query language
- nested relations
- relational model
- normal form
- relational algebra
- database
- object oriented
- relational operators
- keyword search
- data model
- xml data
- structured query language
- hierarchical data
- sql queries
- recursive queries
- relational data model
- expressive power
- constraint databases
- functional dependencies
- query evaluation
- databases
- xml databases
- relational calculus
- xml documents
- relational data
- database technology
- transitive closure
- relational database systems
- database query languages
- complex objects
- relational query languages
- conjunctive queries
- data dependencies
- database schema
- regular expressions
- hierarchical structure
- semantic web
- special case