Keyphrases
- relational algebra
- database query languages
- relational model
- relational calculus
- null values
- relational databases
- normal form
- query language
- data model
- aggregate functions
- relational data model
- expressive power
- functional dependencies
- conceptual model
- structured query language
- database technology
- relational database systems
- inclusion dependencies
- databases
- incomplete information
- database systems
- computational properties
- data exchange
- database design
- database
- sparql queries
- sql queries
- formal semantics
- database language
- database management
- complex objects
- first order logic
- semantic information
- data integration
- definition language
- type checking
- knowledge base
- cd rom
- object oriented databases
- entity relationship
- database applications
- data types
- query answering
- integrity constraints