Only the kind of RIF formulas are allowed which can be obtained by applying the ObjectLogic to RIF/XML transformation on a valid ObjectLogic formula. For example, disjunctions are allowed only in implication conditions since a disjunction in a rule head or a fact is disallowed in ObjectLogic. As "syntactic sugar" groups are allowed but are mapped to conjunctions. rif:local constants may be used but are handled in a special way, see below.