Abstract: Checking OCL Constraints in Distributed Systems Using J2EE/EJB Achim D. Brucker and Burkhart Wolff We present a pragmatic approach using formal methods to increase the quality of distributed component based systems: Based on UML class diagrams annotated with OCL constraints, code for runtime checking of components in J2EE/EJB is automatically generated. Thus, a UML-model for a component can be used in a black-box test for the component. Further we introduce different design patterns for EJBs, which are motivated by different levels of abstraction, and show that these patterns work smoothly together with our OCL constraint checking. A prototypic implementation of the code generator, supporting our design patterns with OCL support, has been integrated into a commercial software development tool.