  Place bisimilarity is a behavioral equivalence for finite Petri nets,
proposed by Schnoebelen and co-workers in 1991. Differently from all the other
behavioral relations proposed so far, a place bisimulation is not defined over
the markings of a finite net, rather over its places, which are finitely many.
However, place bisimilarity is not coinductive, as the union of place
bisimulations may be not a place bisimulation. Place bisimilarity was claimed
decidable in [1], even if the algorithm used to this aim [2] does not
characterize this equivalence, rather the unique maximal place bisimulation
which is also an equivalence relation; hence, its decidability was not proved.
Here we show that it is possible to decide place bisimilarity with a simple,
yet inefficient, algorithm, which essentially scans all the place relations
(which are finitely many) to check whether they are place bisimulations.
Moreover, we propose a slightly coarser variant, we call d-place bisimilarity,
that we conjecture to be the coarsest equivalence, fully respecting causality
and branching time, to be decidable on finite Petri nets.
