Many of today's development and manufacturing projects are so complex that they cannot be conducted only by one company anymore. Such collaborations are mostly modeled and executed using business processes. Business processes are increasingly controlled automatically by IT-systems, but they still consist of many tasks that have to be performed by people. Collaborations using business process are are widely discussed in the context of choreographies and subprocesses. However, collaborations on human task level are discussed much less. The goal of this work is to lay a foundation of a cross-organizational federated task management infrastructure, which supports collaborations on task level.