On the one hand, the inclusion problem for nonerasing and erasing pattern languages is undecidable; see JSSY95]. On the other hand, the language equivalence problem for NE-pattern languages is trivially decidable (see Ang80a]) but the question of whether the same holds for E-pattern languages is still open. It has been conjectured by Jiang et al. JSSY95] that the language equivalence problem fo...
