A Client-Server Protocol for the Composition of Petri Nets

Modelling the behavior of a system as a set of cooperating nets requires to define a high-level communication protocol which takes into account the very nature of their interactions. This paper proposes to adapt the client-server protocol promoted by the object-oriented approach to Petri nets, and to compose Petri nets according to this protocol.This protocol relies upon four basic rules which assert the honesty and discretion of clients and servers. A class of nets respecting these rules, called clientserver nets, is defined, as is the composition of these nets according to a Use function. The possibility to compose client-server nets while preserving the nets' language and liveness is studied. This possibility comes down to very simple relationships between the main characteristics of client-server nets: the demand and the confidence degree as a client, and the supply and the reliability degree as a server. These relationships are preserved by the composition of nets, so the client-server protocol allows for the incremental design of systems and favors the reuse of nets.1