OIL (Ontology Inference Layer
or Ontology Interchange Language
) can be regarded as an Ontology Infrastructure for the Semantic Web
(see paper "OIL: An Ontology Infrastructure for the Semantic Web", IEEE INTELLIGENT SYSTEMS, MARCH/APRIL 2001).
From an theoretic view, OIL is one of the latest Description Logic
Much of the work in OIL has now been incorporated into OWL.
See also: Description Logic, DAML, DAML+OIL