Implementing Business Policies Based on a Framework of Rule Patterns

Application development has to cope with frequently changing requirements which are to a large extent due to changes in the business environment [Loucopoulos et al. 1991]. These facets of business environments are often referred to as business policies. They may be based on ethics, law, culture and organizational commitments by either prescribing a certain action or by constraining the set of possible actions [Odell 1994]. Two main problems arise in the context of implementing business policies. Firstly, business policies are often blurred with code for implementing the basic, unchanging functionality of an application. This makes it difficult to cope with their dynamic nature. This problem can be resolved by factorising out business policies from single applications and representing them in terms of Event/Condition/Action rules (ECA rules). These rules allow the designer to monitor situations represented by events together with conditions and execute the corresponding actions when the events occur and the conditions are true. ECA rules may be stored as first-class objects in so-called active object-oriented database systems [Kappel et al. 1994]. The second problem concerns reusability. Application designers have to decide on the implementation of a particular business policy over and over again for each application domain since appropriate abstraction mechanisms are not available. This problem can be captured by introducing a framework of rule patterns that describes business policies in an abstract way [Kappel et al. 1996].