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Logic Programming - Datalog
- Datalog is a syntactic subset of Prolog
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Originally a rule and query language for deductive databases
- Considers knowledge bases to have two parts
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Extensional Database (EDB) consists of facts
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Intentional Database(IDB) consists of non-ground rules
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Restrictions:
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Datalog disallows function symbols
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Imposes stratification restrictions on the use of recursion + negation
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Allows only range restricted variables ( safe variables )
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- Safe Variables:
- Only allows range restricted variables, i.e. each variable in the conclusion of a rule must also appear in a not negated clause in the premise of this rule.
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This limits evaluation of variables to finitely many possible bindings