TBE: A Graphical Interface for Writing Trigger Rules in Active Databases

Triggers have been adopted as an important database feature and implemented by most major database vendors. Despite their diverse potential usages, one of the obstacles that hinder the trig-gers from their wide deployment is the lack of tools that aid users to create trigger rules. Similar to understanding and specifying database queries in SQL3, it is di cult to visualize the meaning of the written trigger rules. Furthermore, it is even more di cult to write trigger rules using such text-based trigger rule language as SQL3. On the other hand, QBE (Query-By-Example) has been very popular as a user interface forcreating queries in an interactive manner since its introduction decades ago. It is being used in most modern database products in its disguised form. QBE simpli es database query understanding and speci cation by helping the users visualize the querying process. Following the same philosophy, in [LMC 99], we proposed TBE (Trigger-By-Example), a graphical trigger rule speci cation language and system, to help the users understand and specify active database triggers. Since TBE borrowed its basic idea from QBE, it retained the much bene ts of QBE while extending the features to support triggers. Hence, TBE is a useful tool for novice users to create simple triggers in a visual and intuitive manner. Further, since TBE is designed to insulate the details o