Resolving Feature Interaction with Precedence Lists in the Feature Language Extensions

With existing general purpose programming languages, interacting features executed in the same process must be implemented by changing the code of one another [1]. The Feature Language Extensions (FLX) is a set of programming language constructs that enables the programmer to develop interacting features as separate and reusable program modules. Features are integrated and have their interactions resolved in feature packages. FLX provides the precedence list facilities for the programmer to specify the execution order of the features in a feature package. While not applicable in all situations, precedence lists can be used to resolve many interaction conditions in a single statement. This paper describes the two types of precedence lists supported by FLX and their usage. We give the contradiction conditions that may occur when multiple precedence lists are used in a feature package and show how to resolve them. Finally, we show that the two types of FLX precedence lists are primitive: they can be used to implement arbitrary precedence relations among features that do not exhibit contradictions.