Software product lines (SPLs) enable modular, large-scale reuse through a software architecture addressing multiple core and varying features. To reap the benefits of SPLs, their designs need to be stable. Design stability encompasses the sustenance of the product line's modularity properties in the presence of changes to both the core and varying features. It is usually assumed that aspect-oriented programming promotes better modularity and changeability of product lines than conventional variability mechanisms, such as conditional compilation. However, there is no empirical evidence on its efficacy to prolong design stability of SPLs through realistic development scenarios. This paper reports a quantitative study that evolves two SPLs to assess various design stability facets of their aspect-oriented implementations. Our investigation focused upon a multi-perspective analysis of the evolving product lines in terms of modularity, change propagation, and feature dependency. We have identified a number of scenarios which positively or negatively affect the architecture stability of aspectual SPLs.

https://twiki.cin.ufpe.br/twiki/pub/SPG/GenteAreaPublications/ICSE08_figueiredo.pdf

Evolving software product lines with aspects: an empirical study on design stability

There is a growing consensus that crosscutting concerns harm code quality. An example of a crosscutting concern is a functional requirement whose implementation is distributed across multiple software modules. We asked the question, "How much does the amount that a concern is crosscutting affect the number of defects in a program?" We conducted three extensive case studies to help answer this question. All three studies revealed a moderate to strong statistically significant correlation between the degree of scattering and the number of defects. This paper describes the experimental framework we developed to conduct the studies, the metrics we adopted and developed to measure the degree of scattering, the studies we performed, the efforts we undertook to remove experimental and other biases, and the results we obtained. In the process, we have formulated a theory that explains why increased scattering might lead to increased defects.

/pdf/do-crosscutting-concerns-cause-defects-34vyf4qbeo.pdf

Do Crosscutting Concerns Cause Defects

Although one of the main promises of aspect-oriented (AO) programming techniques is to promote better software changeability than objectoriented (OO) techniques, there is no empirical evidence on their efficacy to prolong design stability in realistic development scenarios. For instance, no investigation has been performed on the effectiveness of AO decompositions to sustain overall system modularity and minimize manifestation of ripple-effects in the presence of heterogeneous changes. This paper reports a quantitative case study that evolves a real-life application to assess various facets of design stability of OO and AO implementations. Our evaluation focused upon a number of system changes that are typically performed during software maintenance tasks. They ranged from successive re-factorings to more broadly-scoped software increments relative to both crosscutting and non-crosscutting concerns. The study included an analysis of the application in terms of modularity, change propagation, concern interaction, identification of ripple-effects and adherence to well-known design principles.

/pdf/on-the-impact-of-aspectual-decompositions-on-design-3osq09vutz.pdf

On the impact of aspectual decompositions on design stability: an empirical study

After more than 10 years, Aspect-Oriented Programming (AOP) is still a controversial idea. While the concept of aspects appeals to everyone's intuitions, concrete AOP solutions often fail to convince researchers and practitioners alike. This discrepancy results in part from a lack of an adequate theory of aspects, which in turn leads to the development of AOP solutions that are useful in limited situations. We propose a new theory of aspects that can be summarized as follows: concerns are latent topics that can be automatically extracted using statistical topic modeling techniques adapted to software. Software scattering and tangling can be measured precisely by the entropies of the underlying topic-over-files and files-over-topics distributions. Aspects are latent topics with high scattering entropy. The theory is validated empirically on both the large scale, with a study of 4,632 Java projects, and the small scale, with a study of 5 individual projects. From these analyses, we identify two dozen topics that emerge as general-purpose aspects across multiple projects, as well as project-specific topics/concerns. The approach is also shown to produce results that are compatible with previous methods for identifying aspects, and also extends them. Our work provides not only a concrete approach for identifying aspects at several scales in an unsupervised manner but, more importantly, a formulation of AOP grounded in information theory. The understanding of aspects under this new perspective makes additional progress toward the design of models and tools that facilitate software development.

/pdf/a-theory-of-aspects-as-latent-topics-2515ly5l1r.pdf

A theory of aspects as latent topics

One of the main promises of aspect-oriented programming (AOP) is to promote improved modularization of crosscutting concerns, thereby enhancing the software stability in the presence of changes. This paper presents a quantitative study that assesses the positive and negative effects of AOP on typical maintenance activities of a Web information system. The study consists of a systematic comparison between the object-oriented and the aspect-oriented versions of the same application in order to assess to what extent each solution provides maintainable software decompositions. Our analysis was driven by fundamental modularity attributes, such as coupling, cohesion, conciseness, and separation of concerns. We have found that the aspect-oriented design has exhibited superior stability and reusability through the changes, as it has resulted in fewer lines of code, improved separation of concerns, weaker coupling, and lower intra-component complexity.

Quantifying the Effects of Aspect-Oriented Programming: A Maintenance Study

Exceptions and aspects: the devil is in the details

It is usually assumed that the implementation of exception handling can be better modularized by the use of aspect-oriented programming (AOP). However, the trade-offs involved in using AOP with this goal are not well-understood. This paper presents an in-depth study of the adequacy of the AspectJ language for modularizing exception handling code. The study consisted in refactoring existing applications so that the code responsible for implementing heterogeneous error handling strategies was moved to separate aspects. We have performed quantitative assessments of four systems - three object-oriented and one aspect-oriented - based on four quality attributes, namely separation of concerns, coupling, cohesion, and conciseness. Our investigation also included a multi-perspective analysis of the refactored systems, including (i) the reusability of the aspectized error handling code, (ii) the beneficial and harmful aspectization scenarios, and (iii) the scalability of AOP to aspectize exception handling in the presence of other crosscutting concerns.

/pdf/exceptions-and-aspects-the-devil-is-in-the-details-4mwa9qqtih.pdf

Raquel Maranhão

Papers

Exceptions and aspects: the devil is in the details

Exceptions and aspects: the devil is in the details