Syntactically, RIF-Core has a number of Datalog extensions to support features such as objects and frames as in F-logic <nowiki>[</nowiki>[[#ref-flogic-95|KLW95]]], internationalized resource identifiers (or IRIs, defined by <nowiki>[</nowiki>[[#ref-rfc-3987|RFC-3987]]]) as identifiers for concepts, and XML Schema datatypes <nowiki>[</nowiki>[[#ref-xml-schema2|XML-SCHEMA2]]].