Abstract
To ease the development of distributed systems, the visual notions for the structural aspects of object-oriented analysis and design should be combined with techniques handling concurrency and distribution. A novel approach and language for the visual design of distributed software systems is introduced and illustrated by means of an example.The language of OCoNs - Object Coordination Nets - is integrated into the structuring mechanisms of the UML standard for object-oriented analysis and design. Such an object-oriented notation is crucial for handling complex software systems and can be extended with the graphical expressive power of Petri-Nets to also describe concurrency and coordination. The same visual language is used to specify the interfaces and contracts of software components, the resource handling within a component as well as the control flow of services.