Skolem constant

The first expression creates an anonymous instance, or Skolem constant, from the class Steroid at run time, denoted by the underscore and an instance number. These anonymous instances are also created for the Spectrum and the Descriptor. A named instance can be created by... 

In step 1 the WM is initialised. When execution begins only the antecedent of the rule, Get A tomBasisSet, can be matched by the single fact in the WM. This causes the rule to fire and its consequents to be added to the WM. The instantiated value of ABS is an example of a Skolem constant. (A Skolem constant is normally used to replace an existentially quantified variable in a predicate.) The actual value of ABS is of no interest to us. We choose to instantiate it to the unique but arbitary value ABSl. 

However, it is required in order to establish a property of the output matrix D. As such, this existentially quantified matrix, which is another example of a Skolem constant, is not recorded in the facts part of the WM, but only in the properties part. 

Finally, we illustrated the operation of a goal directed inference system. We showed how its WM must be partitioned into two parts. One partition contains instantiated variables which represent the current state of the ADTs while the other records currently established properties. The role of Skolem constants in the WM was also highlighted. 

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See also in sourсe #XX -- [ ]

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