=== Base Template !DifferenceOf2Classes ===

[[br]]!DifferenceOf2Classes is a template for expressing that a class is the difference, as given in ISO 15926-2, of two classes. 
[[br]]
[[br]]!DifferenceOf2Classes(a, b, c) means that c is the difference of a and b. 
[[br]]
[[br]]Roles: 
[[br]]1 hasClass1 Class 
[[br]]2 hasClass2 Class 
[[br]]3 hasClassDifference Class 

Axiom: 
{{{
DifferenceOf2Classes(x1, x2, x3) <-> 
Class(x1) & 
Class(x2) & 
Class(x3) & 
exists y(EnumeratedSetOf2Classes(x1, x2, y) & 
DifferenceOfSetOfClassTemplate(y, x3)) . 
}}}

NOTE ISO 15926-2 defines the difference of two classes a and b as (a [ b)n(a \ b). See 8.3 for further information on the representation used in this template.