Patterns and XPDL: A Critical Evaluation of the XML Process Definition Language

XML Process Definition Language (XPDL) is the language proposed by the Workflow Management Coalition (WfMC) to interchange process definitions between different workflow products. The goal of XPDL is to provide a Lingua Franca for the workflow domain allowing for the import and export process definitions between a variety of tools ranging from workflow management systems to modeling and simulation tools. Staring point of XPDL is a minimal set of constructs present in most workflow products. Unfortunately, this minimal set does not offer direct support to many of the workflow patterns encountered in practice and present in more mature workflow products. To address this problem, XPDL offers vendor specific extensions. However, this approach definitely does not result in a Lingua Franca. Moreover, to date, even the semantics of the core constructs of XPDL remain undefined. This paper will analyze XPDL using a set of 20 basic workflow patterns and expose some of the semantic problems.