Delta-Oriented Programming of Software Product Lines

Abstract

Feature-oriented programming (FOP) implements software product lines by composition of feature modules. It relies on the principles of stepwise development. Feature modules are intended to refer to exactly one product feature and can only extend existing implementations. To provide more flexibility for implementing software product lines, we propose delta-oriented programming (DOP) as a novel programming language approach. A product line is represented by a core module and a set of delta modules. The core module provides an implementation of a valid product that can be developed with well-established single application engineering techniques. Delta modules specify changes to be applied to the core module to implement further products by adding, modifying and removing code. Application conditions attached to delta modules allow handling combinations of features explicitly. A product implementation for a particular feature configuration is generated by applying incrementally all delta modules with valid application condition to the core module. In order to evaluate the potential of DOP, we compare it to FOP, both conceptually and empirically.

Variability Modelling in the ABS Language

“…Delta-oriented programming was introduced by Schaefer et al [32,34,33] as a novel programming language approach for software-based product lines, and as an direct alternative to feature-oriented programming [3]. Both approaches aim at automatically generating software products for a given feature selection by providing a flexible and modular technique to build different products that share common code.…”

“…In feature-oriented programming, software modules are associated to features, and product generation consists of composing the modules for a feature selection. In delta-oriented programming [32], application conditions over the set of features and their attributes, are associated with modules of program modifications (add, remove or modify code), called delta modules. The collection of applicable delta modules is given by the application conditions that are true for a particular feature and attribute selection.…”

“…The implementation of a software product line in delta-oriented programming [32] is divided into a core module and a set of delta modules. The core module consists of the classes that implement a complete product of the corresponding product line.…”

“…The choice of which delta modules to apply is based on the selection of desired features for the final product. Schaefer et al described and implemented delta-oriented programming for Java [32], introducing the programming language DeltaJava. This language has strongly influenced our design, though we further separate deltas from features by moving application conditions out of deltas and into a product line configuration language, as pursued in [34,33].…”

“…The micro textual variability language (µTVL), based on TVL [7,11], expresses variability via feature models (Section 2). The Delta Modelling Language (DML), based on the concept of delta modelling [32], expresses the code-level variability of ABS models (Section 3). In delta modelling, a set of products is described by an initial core module, which is a Core ABS model, together with a set of product deltas specifying transformations to this core module (additions, removals, or modifications).…”