Abstract
Competitive markets force companies to minimize their costs while at the same time offering solutions which are tailored to the needs of their customers. This requires organizations to outsource at least parts of the overall effort and to rely on services which have to be provided by external partners, leading ultimately to virtual enterprises. The workflow concept has been very successful in coordinating and streamlining business processes but is so far limited to a single organization. Any attempt to distribute workflows among different organizations has to face the problems posed by the complex relationship among autonomous organizations and their services. To address these problems we propose a serviceoriented model for cross-organizational workflows. Modeling the workflow execution as a cooperation of services allows different organizations to interact via well-defined interfaces. We further show how the execution can be optimized by selecting services depending on their contribution to quality criteria of the workflow.

[]