An orthogonal access modifier model for feature-oriented programming

Abstract

In feature-oriented programming (FOP), a programmer decomposes a program in terms of features. Ideally, features are implemented modularly so that they can be developed in isolation. Access control is an important ingredient to attain feature modularity as it provides mechanisms to hide and expose internal details of a module's implementation. But developers of contemporary feature-oriented languages did not consider access control mechanisms so far. The absence of a well-defined access control model for FOP breaks the encapsulation of feature code and leads to unexpected and undefined program behaviors as well as inadvertent type errors, as we will demonstrate. The reason for these problems is that common object-oriented modifiers, typically provided by the base language, are not expressive enough for FOP and interact in subtle ways with feature-oriented language mechanisms. We raise awareness of this problem, propose three feature-oriented modifiers for access control, and present an orthogonal access modifier model.