The Uniqueness Principle for Variables

Currently, the Uniqueness Principle, that every entity represented in the network is represented by a unique node, is not enforced by SNePS for variables. Therefore, it is advised that the Uniqueness Principle for variables be followed by the SNePSUL user as a matter of style. This should be done as follows. Every restriction R used in a restricted quantifier should have a series of variables, Every rule that uses R once should use as its variable. A rule that uses the restriction R more than once should use in the first use of R, in the second use of R, etc. This can be done by using the $ macro to create each variable node the first time the restriction occurs, and the * macro on all subsequent occasions, including subsequent rules. For example, the two rules ``Every dog is a pet'' and ``Every dog hates every cat'' might be entered as follows, assuming that the restrictions Dog(x) and Cat(y) have not previously been used in the network:

 

      		(assert 		forall 		$dog1

      		        		ant    		(build member *dog1 class dog)

      		        		cq     		(build member *dog1 class pet))

      		(assert 		forall 		(*dog1 $cat1)

      		        		&ant  		((build member *dog1 class dog)

      		        		       		 (build member *cat1 class cat))

      		        		cq     		(build agent *dog1 act hates object *cat1))