An empirical investigation into contributory factors of change and fault propensity in large-scale commercial object-oriented software

This thesis was submitted for the degree of Doctor of Philosophy and was awarded by Brunel UniversityObject-Oriented design and development dominates both commercial and open source software projects. One of the principal goals of object-oriented design is to aid reuse, and hence, reduce future maintenance efforts of software systems. However, the on-going maintenance of large-scale software systems (both changes and faults) continues to be a significant proportion of the lifecycle of the system and the total investment cost. Understanding and thus being able to predict - or even reduce - the impact of the contributing factors of future maintenance efforts of a software system is thus highly beneficial to software practitioners. In this Thesis we empirically study a large, commercial software system with the principal aim to determine the contributing factors to the change and fault propensity over a three-year period. We consider the object-oriented design context of the software, specifically its inheritance characteristics, coupling and cohesion properties, object-oriented design pattern participation, and size. We also explore the effect of refactoring and test classes in the software. Our results show that several aspects of the design context of a class have an impact to the change and fault-proneness of the software. Specifically, we show that classes with high afferent or efferent coupling are more change and fault-prone; we also identify a number of design patterns whose participants tend to have a higher change and fault propensity than non-participants and we identify a range of inheritance characteristics (in terms of depth of inheritance and number of children) that result in an increase to change and fault-proneness. Furthermore we show that refactoring is a commonly occurring maintenance activity, although it is largely limited to simpler types of refactorings. Finally, we provide some insight into the co-evolution of production and test code during refactoring

30 Years of Software Refactoring Research:A Systematic Literature Review

Due to the growing complexity of software systems, there has been a dramatic increase and industry demand for tools and techniques on software refactoring in the last ten years, defined traditionally as a set of program transformations intended to improve the system design while preserving the behavior. Refactoring studies are expanded beyond code-level restructuring to be applied at different levels (architecture, model, requirements, etc.), adopted in many domains beyond the object-oriented paradigm (cloud computing, mobile, web, etc.), used in industrial settings and considered objectives beyond improving the design to include other non-functional requirements (e.g., improve performance, security, etc.). Thus, challenges to be addressed by refactoring work are, nowadays, beyond code transformation to include, but not limited to, scheduling the opportune time to carry refactoring, recommendations of specific refactoring activities, detection of refactoring opportunities, and testing the correctness of applied refactorings. Therefore, the refactoring research efforts are fragmented over several research communities, various domains, and objectives. To structure the field and existing research results, this paper provides a systematic literature review and analyzes the results of 3183 research papers on refactoring covering the last three decades to offer the most scalable and comprehensive literature review of existing refactoring research studies. Based on this survey, we created a taxonomy to classify the existing research, identified research trends, and highlighted gaps in the literature and avenues for further research.Comment: 23 page

30 Years of Software Refactoring Research: A Systematic Literature Review

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/155872/4/30YRefactoring.pd

Understanding Variability-Aware Analysis in Low-Maturity Variant-Rich Systems

Context: Software systems often exist in many variants to support varying stakeholder requirements, such as specific market segments or hardware constraints. Systems with many variants (a.k.a. variant-rich systems) are highly complex due to the variability introduced to support customization. As such, assuring the quality of these systems is also challenging since traditional single-system analysis techniques do not scale when applied. To tackle this complexity, several variability-aware analysis techniques have been conceived in the last two decades to assure the quality of a branch of variant-rich systems called software product lines. Unfortunately, these techniques find little application in practice since many organizations do use product-line engineering techniques, but instead rely on low-maturity \clo~strategies to manage their software variants. For instance, to perform an analysis that checks that all possible variants that can be configured by customers (or vendors) in a car personalization system conform to specified performance requirements, an organization needs to explicitly model system variability. However, in low-maturity variant-rich systems, this and similar kinds of analyses are challenging to perform due to (i) immature architectures that do not systematically account for variability, (ii) redundancy that is not exploited to reduce analysis effort, and (iii) missing essential meta-information, such as relationships between features and their implementation in source code.Objective: The overarching goal of the PhD is to facilitate quality assurance in low-maturity variant-rich systems. Consequently, in the first part of the PhD (comprising this thesis) we focus on gaining a better understanding of quality assurance needs in such systems and of their properties.Method: Our objectives are met by means of (i) knowledge-seeking research through case studies of open-source systems as well as surveys and interviews with practitioners; and (ii) solution-seeking research through the implementation and systematic evaluation of a recommender system that supports recording the information necessary for quality assurance in low-maturity variant-rich systems. With the former, we investigate, among other things, industrial needs and practices for analyzing variant-rich systems; and with the latter, we seek to understand how to obtain information necessary to leverage variability-aware analyses.Results: Four main results emerge from this thesis: first, we present the state-of-practice in assuring the quality of variant-rich systems, second, we present our empirical understanding of features and their characteristics, including information sources for locating them; third, we present our understanding of how best developers\u27 proactive feature location activities can be supported during development; and lastly, we present our understanding of how features are used in the code of non-modular variant-rich systems, taking the case of feature scattering in the Linux kernel.Future work: In the second part of the PhD, we will focus on processes for adapting variability-aware analyses to low-maturity variant-rich systems.Keywords:\ua0Variant-rich Systems, Quality Assurance, Low Maturity Software Systems, Recommender Syste

Identifying Crosscutting Concerns Using Fan-in Analysis

Aspect mining is a reverse engineering process that aims at finding crosscutting concerns in existing systems. This paper proposes an aspect mining approach based on determining methods that are called from many different places, and hence have a high fan-in, which can be seen as a symptom of crosscutting functionality. The approach is semi-automatic, and consists of three steps: metric calculation, method filtering, and call site analysis. Carrying out these steps is an interactive process supported by an Eclipse plug-in called FINT. Fan-in analysis has been applied to three open source Java systems, totaling around 200,000 lines of code. The most interesting concerns identified are discussed in detail, which includes several concerns not previously discussed in the aspect-oriented literature. The results show that a significant number of crosscutting concerns can be recognized using fan-in analysis, and each of the three steps can be supported by tools.Comment: 34+4 pages; Extended version [Marin et al. 2004a

Consolidation of Customized Product Copies into Software Product Lines

In software development, project constraints lead to customer-specific variants by copying and adapting the product. During this process, modifications are scattered all over the code. Although this is flexible and efficient in the short term, a Software Product Line (SPL) offers better results in the long term, regarding cost reduction, time-to-market, and quality attributes. This book presents a novel approach named SPLevo, which consolidates customized product copies into an SPL

The state of adoption and the challenges of systematic variability management in industry

Handling large-scale software variability is still a challenge for many organizations. After decades of research on variability management concepts, many industrial organizations have introduced techniques known from research, but still lament that pure textbook approaches are not applicable or efficient. For instance, software product line engineering—an approach to systematically develop portfolios of products—is difficult to adopt given the high upfront investments; and even when adopted, organizations are challenged by evolving their complex product lines. Consequently, the research community now mainly focuses on re-engineering and evolution techniques for product lines; yet, understanding the current state of adoption and the industrial challenges for organizations is necessary to conceive effective techniques. In this multiple-case study, we analyze the current adoption of variability management techniques in twelve medium- to large-scale industrial cases in domains such as automotive, aerospace or railway systems. We identify the current state of variability management, emphasizing the techniques and concepts they adopted. We elicit the needs and challenges expressed for these cases, triangulated with results from a literature review. We believe our results help to understand the current state of adoption and shed light on gaps to address in industrial practice.This work is supported by Vinnova Sweden, Fond Unique Interminist´eriel (FUI) France, and the Swedish Research Council. Open access funding provided by University of Gothenbur

Refactorings to evolve object-oriented systems with aspect-oriented concepts

Tese de doutoramento em Informática.Software engineering tools should support complete separation of concerns, by enabling the deployment of each different concern in its own unit of modularity. Unfortunately, current tools and languages – including those supporting the object-oriented programming paradigm – fail to provide a complete and effective support for the separation of all concerns. Undesirable phenomena such as code scattering and code tangling ensue. Aspect-Oriented Programming is a new programming paradigm capable of modularising crosscutting concerns. Aspect-oriented programming complements existing programming paradigms, including object-oriented programming, with constructs that provide a fuller separation of concerns. Refactoring is a technique to restructure program source code in order to improve its underlying design and style while preserving the externally observable behaviour. “Code smells” help to detect inadequate structures and designs, which are then gradually removed through refactoring processes. There is a prospect of aspect-oriented programming becoming a mainstream technology in the near future. This begs the question of how to deal with a large base of object-oriented legacy code when aspect-orientation becomes standard practice. AspectJ's backward compatibility with Java opens the way for refactoring existing Java applications to leverage the concepts and mechanisms of aspects. This requires a prior idea of good style for aspect-oriented source code, something yet to be developed and matured. This thesis contributes to the definition of a new style appropriate to aspect orientation. To this effect, this thesis documents a collection of novel refactorings enabling the extraction of crosscutting concerns from object-oriented legacy source code and the subsequent restructuring of the aspects thus obtained. In addition, this thesis presents a review of traditional object-oriented code smells so they can be used as indicators of latent aspects in object-oriented source code. Finally, this thesis proposes several novel aspect-oriented code smells. We validate the refactorings through an illustrative refactoring process.Idealmente, as ferramentas de engenharia de programas suportariam uma estrita separação de facetas, possibilitando a colocação de cada faceta na sua própria unidade modular. Infelizmente, as actuais ferramentas e linguagens – incluindo as que suportam o paradigma da orientação ao objecto – não conseguem obter uma completa e efectiva separação de todas as facetas. Daí resultam fenómenos indesejáveis tais como a dispersão e emaranhado de texto fonte. A programação orientada ao aspecto é um novo paradigma da programação capaz de modularizar facetas transversais. A orientação ao aspecto complementa os paradigmas existentes, incluindo a orientação ao objecto, com mecanismos que providenciam uma separação de facetas mais completa. A refabricação de programas é uma técnica para reestruturar o texto fonte de um programa no sentido de melhorar a concepção e estilo subjacentes, mantendo o seu comportamento externamente observável. “Maus cheiros” no texto fonte ajudam a detectar estruturas e concepções inadequadas, que são então gradualmente removidos através de processos de refabricação. Existe a perspectiva da orientação ao aspecto ter uma aceitação generalizada no futuro próximo. Coloca-se a questão de como lidar com uma grande base instalada de texto fonte orientado ao objecto legado quando tal acontecer. A compatibilidade retroactiva de AspectJ em relação a Java possibilita a refabricação das aplicações Java existentes de modo a tomarem partido dos conceitos e mecanismos dos aspectos. Porém, isto tem como pressuposto uma ideia clara de bom estilo para o texto fonte orientado ao aspecto, algo que actualmente não existe duma maneira desenvolvida e matura. Esta tese contribui para a caracterização de um novo estilo, apropriado à orientação ao aspecto. Para esse efeito, esta tese documenta uma colecção de refabricações originais através das quais facetas transversais existentes em texto legado orientado ao objecto são extraídas para aspectos, e a posterior reestruturação dos aspectos assim obtidos pode ser realizada. Esta tese apresenta também uma reapreciação dos maus cheiros orientados ao objecto tradicionais no sentido de poderem ser usados na detecção de aspectos latentes no texto fonte orientado ao objecto. Por fim, esta tese propõe diversos maus cheiros originais, orientados ao aspecto. As refabricações são validadas por meio de um processo de refabricação ilustrativo.Programa de Desenvolvimento Educativo para Portugal III (PRODEP III) - (Medida 5 - Acção 5.3 - Eixo 3 - Formação Avançada de Docentes do Ensino Superior).Portable Parallel Computing based on Virtual Machines (PPC-VM) - (PO-SI/CHS/47158/2002).Fundação Luso Americana para o Desenvolvimento (FLAD)