Intersection closure of L(nrNIDPDAwtl)

Determine whether the language family L(nrNIDPDAwtl), consisting of all languages accepted by non-returning nondeterministic input-driven pushdown automata with translucent input letters, is closed under intersection when automata may have incompatible signatures, without assuming signature compatibility.

Background

The paper presents non-closure under intersection for the returning nondeterministic class L(NIDPDAwtl), even with regular languages, but does not settle the intersection closure for the non-returning counterpart L(nrNIDPDAwtl).

As with union, closure under intersection is immediate if devices use compatible signatures; the open question asks for the general case without compatible signatures.