During my visit at the University of Oldenburg (Germany) in May 1995 in the group of Prof. Hans Fleischhack (within the PROCOPE project POEM), I became interested in an alternative to the equivalence by duplication on labeled Petri nets, such as used in Petri-Box Calculus in the definition of Boxes. In almost any process algebra we have the equation ``'' which is true at the semantic level. This is not the case for the PBC. One of the consequences of this unequation is that the operation of iteration does not in general preserve the property of ``1-safeness'' of its arguments. This poses a real problem for implementation.
We have recently proposed a solution to this problem by defining a new structural equivalence on labeled Petri nets [FP97a,FP97b].