An Overview of the gDEEP Calculus

The goal of Feature-oriented Programming (FOP) is to modularize software systems in terms of features. A feature is an increment in functionality and refines the content of other features. A software system typically consists of a collection of different kinds of software artifacts, e.g. source code, build scripts, documentation, design documents, and performance profiles. We and others have noticed a principle of uniformity, which dictates that when composing features, all software artifacts can actually be refined in a uniform way, regardless of what they represent. Previous work did not take advantage of this uniformity; each kind of software artifact used a separate tool for composition, developed from scratch. We present gDEEP, a core calculus for features and feature composition which is language-independent; it can be used to compose features containing any kinds of artifact. This calculus allows us to define general algorithms for feature refinement, composition, and validation. We provide the formal syntax, operational semantics, and type system of gDEEP and explain how different kinds of software artifacts, including Java, Bali, and XML files, can be represented. A prototype tool and three case studies demonstrate the practicality of our approach.