material | (material ?SUBSTANCE ?OBJECT) means that ?OBJECT is structurally made up in part of ?SUBSTANCE. This relation encompasses the concepts of 'composed of', 'made of', and 'formed of'. For example, a particular instance of plastic is a material of my computer monitor. Note that material is a relation between two instances. If one wants to say that a CorpuscularObject is made up of a subclass of Substance, two assertions are necessary. For example, to say that my computer monitor is made out of the Substance plastic, one would write: (instance ThisPlastic Plastic) and (material ThisPlastic MyComputer). Compare 'component' and 'piece', which are also subrelations of part | CorpuscularObject | Substance | (=> (instance ?OBJ CorpuscularObject) (exists (?SUBSTANCETYPE1 ?SUBSTANCETYPE2 ?SUBSTANCE1 ?SUBSTANCE2) (and (subclass ?SUBSTANCETYPE1 Substance) (subclass ?SUBSTANCETYPE2 Substance) (instance ?SUBSTANCE1 ?SUBSTANCETYPE1) (instance ?SUBSTANCE2 ?SUBSTANCETYPE2) (material ?SUBSTANCE1 ?OBJ) (material ?SUBSTANCE2 ?OBJ) (not (equal ?SUBSTANCE1 ?SUBSTANCE2)))))
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