A Note on Occur-Check

Most known results on avoiding the occur-check are based notion of "not subject to occur-check" (NSTO). It means that unification is performed only such pairs atoms for which never succeeds in any run a nondeterministic algorithm. Here we show this requirement too strong. We how weaken it, and present some related sufficient conditions under may be safely omitted. examples proposed approach provides more general than approaches well-moded nicely moded programs (this includes cases latter inapplicable).