Web Service Orchestration with Super-Dual Object Nets

摘要

Refinement of Petri nets is well suited for the hierarchical design of system models. It is used to represent a model at different levels of abstraction. Usually, refinement is a static concept. For some inherent dynamic domains as for example the modelling of web services, we need a more flexible form of refinement, e.g. to bind web services at run-time. Run-time binding allows for a flexible orchestration of services. The requirement of dynamic refinement at run-time is quite strong. Since we would like to redefine the system structure by itself, transition refinement cannot be implemented by a model transformation. Instead, an approach is needed which allows for dynamic net structures that can evolve as an effect of transitions firing. In previous work we introduced nets-within-nets as a formalism for the dynamic refinement of tokens. Here we consider an extension of nets-within-nets that uses special net tokens describing the refinement structure of transitions. Using this formalism it is possible to update refinements, introduce alternative refinements, etc. We present some formal properties of the extended formalism and introduce an example implementation for the tool Renew.