Deductive Databases II
Query languages
- Datalog: DB extension of Prolog
- Logic-based
- vastly different from SQL
- but curiously, both are non-procedural
- “fixpoint”: v is a fixpoint of a function f if f(v)= v
- recognizing and computing fixpoints efficiently is the heart of recursive query processing
- Thorny problem: negation
- What part of “not” don’t you understand?