Reversible computation vs. reversibility in Petri nets

Petri nets are a general formal model of concurrent systems which supports both action-based and state-based modelling and reasoning. One of important behavioural properties investigated in the context of Petri nets has been reversibility, understood as the possibility of returning to the initial marking from any reachable net marking. Thus reversibility in Petri nets is a global property. Reversible computation, on the other hand, is typically a local mechanism by which a system can undo some of the executed actions. This paper is concerned with the modelling of reversible computation within Petri nets. A key idea behind the proposed construction is to add ‘reverses’ of selected transitions, and the paper discusses its different implementations. Adding reverses can severely impact on the behaviour of a Petri net. Therefore it is important, in particular, to be able to determine whether the modified net has a similar set of states as the initial one. We first prove that the problem of establishing whether the initial and modified nets have the same reachable markings is undecidable, even in the restricted case considered in this paper. We then show that the problem of checking whether the reachability sets of the two nets cover the same markings is decidable.