UnionVar: A set (variable or ground) corresponding to the union of the set's elements (sets themselves); GlbU: Set union of the set's glb; PossU: Set of possible union elements with counters (X:N), i.e. an ordered list of all elements in the sets in set's poss (lub\glb) with the number of occurrences attached Singles: Set of elements where N=1 in PossU