This article explains how to implement the observer pattern in a suite of integrated EJB apps. The suite has a shared repository and each EJB application has it own repository. Every application in the suite runs on a separate host. Each application needs to observe changes in the shared repository as they occur -- and within the transaction in which they occur. If a proposed change to the shared data is unacceptable to any given application then the transaction must be aborted before the change is made permanent.