Two programming paradigms are gaining attention in the overlapping fields of software product lines (SPLs) and incremental software development (ISD). Feature-oriented programming (FOP) aims at large-scale compositional programming and feature modularity in SPLs using ISD. Aspect-oriented programming (AOP) focuses on the modularization of crosscutting concerns in complex software. Although feature modules, the main abstraction mechanisms of FOP, perform well in implementing large-scale software building blocks, they are incapable of modularizing certain kinds of crosscutting concerns. This weakness is exactly the strength of aspects, the main abstraction mechanisms of AOP. We contribute a systematic evaluation and comparison of FOP and AOP. It reveals that aspects and feature modules are complementary techniques. Consequently, we propose the symbiosis of FOP and AOP and aspectual feature modules (AFMs), a programming technique that integrates feature modules and aspects. We provide a set of tools that support implementing AFMs on top of Java and C++. We apply AFMs to a nontrivial case study demonstrating their practical applicability and to justify our design choices.

Feature-Oriented Software Development (FOSD) provides a multitude of formalisms, methods, languages, and tools for building variable, customizable, and extensible software. Along different lines of research different ideas of what a feature is have been developed. Although the existing approaches have similar goals, their representations and formalizations have not been integrated so far into a common framework. We present a feature algebra as a foundation of FOSD. The algebra captures the key ideas and provides a common ground for current and future research in this field, in which also alternative options can be explored.

Software product lines aim to create highly configurable programs from a set of features. Common belief and recent studies suggest that aspects are well-suited for implementing features. We evaluate the suitability of AspectJ with respect to this task by a case study that refactors the embedded database system Berkeley DB into 38 features. Contrary to our initial expectations, the results were not encouraging. As the number of aspects in a feature grows, there is a noticeable decrease in code readability and maintainability. Most of the unique and powerful features of AspectJ were not needed. We document where AspectJ is unsuitable for implementing features of refactored legacy applications and explain why. 1.

Aspect-Oriented Programming (AOP) and Feature-Oriented Programming (FOP) are complementary technologies that can be combined to overcome their individual limitations. Aspectual Mixin Layers (AML) is a representative approach that unifies AOP and FOP. We use AML in a non-trivial case study to create a product line of overlay networks. We also present a set of guidelines to assist programmers in how and when to use AOP and FOP techniques for implementing product lines in a stepwise and generative manner.

Feature-Oriented Programming (FOP) decomposes complex software into features. Features are main abstractions in design and implementation. They reflect user requirements and incrementally refine one another. Although, features crosscut object-oriented architectures they fail to express all kinds of crosscutting concerns. This weakness is exactly the strength of aspects, the main abstraction mechanism of Aspect-Oriented Programming (AOP). In this article we contribute a systematic evaluation and comparison of both paradigms, AOP and FOP, with focus on incremental software development. It reveals that aspects and features are not competing concepts. In fact AOP has several strengths to improve FOP in order to implement crosscutting features. Symmetrically, the development model of FOP can aid AOP in implementing incremental designs. Consequently, we propose the architectural integration of aspects and features in order to profit from both paradigms. We introduce aspectual mixin layers (AMLs), an implementation approach that realizes this symbiosis. A subsequent evaluation and a case study reveal that AMLs improve the crosscutting modularity of features as well as aspects become well integrated into incremental development style.

Feature-oriented programming (FOP) is a paradigm that incorporates programming language technology, program generation techniques, and stepwise refinement. In their GPCE’07 paper, Thaker et al. suggest the development of a type system for FOP to guarantee safe feature composition, i.e, to guarantee the absence of type errors during feature composition. We present such a type system along with a calculus for a simple feature-oriented, Java-like language, called Feature Featherweight Java (FFJ). Furthermore, we explore four extensions of FFJ and how they affect type soundness.

A feature-oriented product line is a family of programs that share a common set of features. A feature implements a stakeholder’s requirement and represents a design decision or configuration option. When added to a program, a feature involves the introduction of new structures, such as classes and methods, and the refinement of existing ones, such as extending methods. A feature-oriented decomposition enables a generator to create an executable program by composing feature code solely on the basis of the feature selection of a user – no other information needed. A key challenge of product line engineering is to guarantee that only well-typed programs are generated. As the number of valid feature combinations grows combinatorially with the number of features, it is not feasible to type check all programs individually. The only feasible approach is to have a type system check the entire code base of the feature-oriented product line. We have developed such a type system on the basis of a formal model of a feature-oriented Java-like language. The type system guaranties type safety for feature-oriented product lines. That is, it ensures that every valid program of a well-typed product line is well-typed. Our formal model including type system is sound and complete.

Feature-Oriented Software Development (FOSD) provides a multitude of formalisms, methods, languages, and tools for building variable, customizable, and extensible software. Along different lines of research, different notions of a feature have been developed. Although these notions have similar goals, no common basis for evaluation, comparison, and integration exists. We present a feature algebra that captures the key ideas of feature orientation and provides a common ground for current and future research in this field, in which also alternative options can be explored.

A functional aspect is an aspect that has the semantics of a transformation; it is a function that maps a program to an advised program. Functional aspects are composed by function composition. In this paper, we explore functional aspects in the context of aspectoriented refactoring. We show that refactoring legacy applications using functional aspects is just as flexible and expressive as traditional aspects (functional aspects can be refactored in any order), while having a simpler semantics (aspect composition is just function composition), and causes fewer undesirable interactions between aspects (the number of potential interactions between functional aspects is half the number of potential interactions between traditional aspects). We analyze several aspect-oriented programs of different sizes to support our claims.

Aspects offer sophisticated mechanisms to modularize crosscutting concerns. Aspect Oriented Programming (AOP) has been successfully applied to many domains; however, its application to product line engineering has not been thoroughly explored. Features are increments in program functionality and are building blocks of software product lines. Work on Feature Oriented Programming (FOP) has shown that a crucial factor to synthesize product lines is composing features by function composition. In this paper we describe a way to emulate function composition using AspectJ for the synthesis of a non-trivial product line, present a general mechanism to support it and highlight its potential reuse benefits. Our study also profiles the role different aspect constructs play in the synthesis of product lines and offers venues of research on the use of aspects in product line implementations. 1