The knowledge base is created using the Protégé ontology editor, and part of it is depicted in Fig. 3 with the Jambalaya plug-in. The squares in the figure represent concepts. An “is-a” relation is represented by placing a square within a bigger one. The connectors between different domains, with CD being false, are represented with bold straight lines, and with CD being true are shown as bold curved lines. The straight lines that link the black squares (instances) are connectors, with CD always false, linking different instances. The knowledge-specifier (“ProductType”) is shown as a rounded square and the arcs that link it to the other concepts are represented by bold dotted lines. THING (the domain within which everything is contained) is the root concept of the ontology.