We discuss the implementation of GOAD (gemstone object-oriented active database), an active object-oriented database built on top of genstone. This system has been veveloped with the specific aim of supporting interface tools for the creation and maintenance of rule bases, and we give particular attention to explaining how goad is designed to meet this aim. We show how objects, classes and metaclasses can support a there leved event model which integrates with the underlying system in an open manner. Moreover, by providing a uniform interface to these different objects, we are providing support for the implementation of more generic tools. We discuss the design of the system and how we gather inherited rules at run-time in an efficient manner. We explain the problems that arise as a result of our desired mode of implementation and how they were circumvented. Finally we discuss our future work and specifically how we plan to implement tools for easier creation of rule bases.