Modeling Object Behavior: To Use Methods or Rules or Both?

. Active object-oriented databases provide two means to model behavior of objects: (1) methods and (2) rules. In many cases methods and rules can be used interchangeably to achieve the same effect. If clear design guidelines are missing and comparable situations are realized differently, information systems can become hard to understand and hard to maintain. Moreover, it is known that large sets of rules tend to lead to non-transparent systems. This paper shows that high-level semantic modeling can significantly help to tackle the rule-method problem. 1 Introduction Active object-oriented databases represent the structure of real-world entities by attributes, their passive behavior by methods, and their active behavior by eventcondition action rules (ECA-rules) [8, 7, 12, 18, 1, 5]. An ECA-rule defines what action is to be taken, if the specified event occurs and the specified condition holds. E.g., "when an item is to be deleted (the event) and orders for that item exist (the conditi..