Universal Marker and Functional Relation: Semantics and Operations
The universal marker (i.e., universal quantifier) and the functional
relation are two useful notations that make Conceptual Graph (CG) representations more concise in expressing universally quantified facts and functional
dependencies, which are commonly used in knowledge bases, logic programs
and data conceptual schemas. We introduce an expansion rule that formally
defines the semantics of CGs containing universal markers and/or functional
relations. On the basis of this formal semantics, we define two reasoning operations that are performed directly on CGs with these two notations to make them
more useful. One operation is the universal CG projection defining the subsump
tion relation on the extended CGs. The other operation is the universal concept
join performing universal instantiations and inheritances simultaneously in one
graph operation. Both the operations are proved to be sound with respect to their described interpretations.