Research efforts in the area of active object-oriented database systems have been put mainly into the development of knowledge models and execution models without considering the consequences for their implementation. Thus, this paper is dedicated to implementation issues within the active objectoriented prototype system TriGS (Triggersystem for Gem-Stone). One emphasis is put on the detection of composite events whose components should be allowed to span not only different transactions, but also different applications. Another emphasis is put on performance issues, in particular for rules which are defined to be executed in parallel. To realize these goals, first, composite event detection as well as rule scheduling is done in parallel to the event signaling application. Second, events which occur within an application transaction are immediately signaled, thus being visible across transaction boundaries. And third, rule processing is made efficient by means of several rule processors, whose number is dynamically controlled.