### Datalog - Notes

The Datalog (function-free) sublanguage of Horn logic is at the semantic
foundation of RuleML.
Datalog is the language in the intersection of SQL and Prolog. It can
thus be considered as the subset of logic programming needed for representing
the information of relational databases, including
(recursive) views. That is, in Datalog we can define facts, corresponding to explicit rows of
relational tables (extensional definition), and rules,
corresponding to tables defined implictly by views (intensional definition).