Petri net schemata are an intuitive and expressive approach to describe high-level Petri nets. A Petri net schema is a Petri net with edges
and transitions inscribed by terms and Boolean expressions, respectively. A concrete high-level net is gained by interpreting
the symbols in the inscriptions by a
structure. The semantics of this high-level net can be described in terms of a
transition system. Therefore, the semantics of a Petri net schema can be conceived as a family of transition systems indexed by structures.
In this paper we characterize the expressive power of a general version of Petri net schemata. For that purpose we examine
families of transition systems in general and characterize the families as generated by Petri net schemata. It turns out that
these families of transition systems can be characterized by simple and intuitive requirements.