2.2 A CG is a bipartite graph
A conceptual graph is a bipartite graph. This simply means that there are no arcs between a concept and another concept, and no arcs between a relation and another relation. All arcs either go from a concept to a relation or from a relation to a concept.
The term "bipartite" means "partitioned in two". The nodes of a bipartite graph can be divided into two nonempty sets A and B, with two different kinds of nodes. All arcs of a bipartite graph then connect exactly one node from A and one node from B. Therefore, all arcs cross the boundary between the two sets of the two kinds of nodes.
Conceptual graphs are bipartite in that it has two kinds of nodes, concepts and relations, and every arc "crosses the border" between the two sets of the two kinds of nodes. That is, any arc connects a concept with a relation.
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