Irredundant set

Irredundant set --- неизбыточное множество (вершин).

A set [math]\displaystyle{ I }[/math] of vertices of [math]\displaystyle{ G }[/math] is an irredundant set, if every vertex [math]\displaystyle{ x }[/math] of [math]\displaystyle{ I }[/math] that is not isolated in [math]\displaystyle{ I }[/math] has at least one external [math]\displaystyle{ I }[/math]-private neighbor (or I-EPN), that is a vertex of [math]\displaystyle{ V - I }[/math] that is adjacent to [math]\displaystyle{ x }[/math] but to no other vertex of [math]\displaystyle{ I }[/math]. The minimum cardinality of the maximal irredundant set is called an irredundance number and denoted by [math]\displaystyle{ ir(G) }[/math]. A vertex is an annihilator of a vertex [math]\displaystyle{ x }[/math] of an irredundant set [math]\displaystyle{ I }[/math] ([math]\displaystyle{ x }[/math] not isolated in [math]\displaystyle{ I }[/math]) if it dominates all the I-EPN's of [math]\displaystyle{ x }[/math].