Decidability of reachability for Pushdown/Grammar VASS

Determine whether the reachability problem for pushdown vector addition systems (Pushdown VASS) and grammar vector addition systems (Grammar VASS) is decidable.

Background

The authors position their results for PVAS as steps toward understanding more general models such as Pushdown/Grammar VASS. They note that PVASS are equivalent to a subclass of Pushdown VASS, suggesting that progress on PVAS could inform the broader decidability question.

The paper explicitly states that the decidability of reachability for Pushdown/Grammar VASS remains an open question, underlining its significance in the theory of computation and verification.