This thesis describes an investigation of the possibility to apply a maintenance concept originally developed for the industry, on software maintenance. Today a large amount of software development models exist but not many of them treat maintenance as a part of the software life cycle. In most cases maintenance is depicted as an activity towards the end of the software life cycle. The high cost ascribed to software maintenance motivates for improvements. The maintenance concept TQMain proposed in this thesis distinguishes from other maintenance concepts by its use of preventive, predictive and proactive maintenance strategies. TQMain uses a common database to store real-time data from various departments and uses it for analyse and assessment to track the development of deviations in the condition of the production process and product quality at an early stage. A continuous cyclic improvement of the maintenance strategy is reached by comparing the data from the real-time measurements with data from the database. The ISO/IEC Software engineering – Product qualities is used as a source of empiric data to conclude that the correct quality characteristics are used for identifying software product quality and its characteristics and compare them with the characteristics of industrial product quality. The results presented are that in the conceptual outline of TQMain measures are obviously not the same as in software maintenance, but the aspect of product quality is common for both. The continuous cyclic improvement of the product quality that TQMain features together with the aspect of detecting potential failures before they occur would, judging from the conceptual outline of TQMain be applicable on software maintenance.

Context. Global software development (GSD) has become a significant practice in software industry due to rapid globalization processes and technological advances. In GSD, software development activities are carried at geographically distributed locations by collaboration of people with different background and culture. In this study, we studied an area of global software maintenance from both of state of the art and state of practice in order to understand which challenges are hampering the effectiveness of distributed maintenance team as well as which mitigation strategies can appease their impact. Objectives. The study unravels challenges of global software maintenance and alleviation strategies to address to those challenges by methodically reviewing relevant studies and industrial practitioners’ experiences. It also explores the convergence and divergence between the outcome from scientific studies and industrial settings Methods. Data collection processes are done through systematic literature review and industrial interviews. In the systematic review a variety of article sources are queried, including Compendex, Inspec, IEEE Xplore, ACM Digital Library, Wiley Inter Science, Scopus, Science Direct, ISI WOS and Springer Link. Interviews are conducted with five practitioners from 4 different multinational organizations. As data analysis methods, grounded theory and qualitative comparative analysis are applied. Results. Totally, 90 different challenges and 73 strategies were revealed. Unlike most of similar studies in GSD which used 3C categorization (Communication, Control and Coordination), we come up with a different view as we called 3PT which conceptualizes challenges and strategies into People, Process, Product and Technology factors. Conclusions. We conclude that collaborative processes and their clear definitions among all maintenance stakeholders are one of the critical success factors of effective maintenance in global collaboration. Most importantly, a maintenance management should focus on the holistic improvement of each factor in 3PT and their synergy can contribute much to the successful software maintenance in globally distributed environment. / We found that collaborative processes and their clear definitions among all maintenance stakeholders are one of the critical success factors of effective maintenance in global collaboration. Most importantly, a maintenance management should focus on the holistic improvement of each factor in 3PT and their synergy can contribute much to the successful software maintenance in globally distributed environment.

An important issue in software evolution is the time and effort needed to understand existing applications. Reverse engineering software to recover behavioural models is difficult and is complicated due to the lack of a standardized way of extracting and visualizing knowledge. In this thesis, we study a technique for automatically extracting static and dynamic data from software, filtering and analysing the data, and visualizing the behavioural model of a selected feature of a software application. We also investigate the usefulness of the generated diagrams as documentation for the software. We present a literature review of studies that have used static and dynamic data analysis for software comprehension. A set of criteria is created, and each approach, including this thesis’ technique, is compared using those criteria. We propose an approach to simplify lengthy traces by filtering out software components that are too low level to give a high-level picture of the selected feature. We use static information to identify and remove small and simple (or uncomplicated) software components from the trace. We define a utility method as any element of a program designed for the convenience of the designer and implementer and intended to be accessed from multiple places within a certain scope of the program. Utilityhood is defined as the extent to which a particular method can be considered a utility. Utilityhood is calculated using different combinations of selected dynamic and static variables. Methods with high utilityhood values are detected and removed iteratively. By eliminating utilities, we are left with a much smaller trace which is then visualized using the Use Case Map (UCM) notation. UCM is a scenario language used to specify and explain behaviour of complex systems. By doing so, we can identify the algorithm that generates a UCM closest to the mental model of the designers. Although when analysing our results we did not identify an algorithm that was best in all cases, there is a trend in that three of the best four algorithms (out of a total of eight algorithms investigated) used method complexity and method lines of code in their parameters. We also validated the algorithm results by doing a comparison with a list of methods given to us by the creators of the software and doing precision and recall calculations. Seven out of the eight participants agreed or strongly agreed that using UCM diagrams to visualize reduced traces is valid approach, with none who disagreed.

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[pt] Características são abstrações-chave para o desenvolvimento e manutenção de linhas de produto de software. Um desafio encarado na manutenção de linhas de produto de software é o entendimento das dependências que existem entre características. No código-fonte, uma dependência entre características ocorre sempre que um elemento de programa dentro dos limites de implementação de uma característica depende de elementos externos a esta característica. Exemplos são atributos ou métodos definidos na implementação de uma característica, mas utilizados no código responsável pela implementação de outra característica. A medida que desenvolvedores modificam o código-fonte associado com uma característica, eles devem garantir que outras características são consistentemente atualizadas com as novas mudanças – as chamadas propagações de mudanças. No entanto, a apropriada propagação de mudanças não é uma tarefa trivial, pois características geralmente não são modularizadas no código-fonte. Dessa forma, dado uma mudança em uma determinada característica, é desafiador revelar quais (partes de) outras características também devem ser alteradas. Propagação de mudanças se torna, portanto, um aspecto central e não-trivial da manutenção de linhas de produto de software. Desenvolvedores podem negligenciar partes importantes de código que deveriam ser revisadas ou alteradas, portanto não propagando mudanças de forma completa. Por outro lado, desenvolvedores também podem analisar de forma desnecessária partes de código que não são relevantes para a tarefa de manutenção de características, portanto aumentando o esforço de manutenção ou até propagando mudanças de forma indevida. A criação de um bom modelo mental da estrutura das dependências de características se torna essencial para ganhar compreensão sobre o complexo relacionamento de características com o objetivo de propagar mudanças de forma apropriada. Infelizmente, não existe entendimento no estado-da-arte sobre propriedades estruturais de dependências de características que afetam a propagação de mudanças. Este entendimento ainda não é possível, pois: (i) não existe meios de caracterização e quantificação para propriedades estruturais de dependências de características, e (ii) não existem investigações empíricas sobre a influência dessas propriedades na propagação de mudanças. Nesse contexto, esta tese apresenta três contribuições para superar os problemas acima mencionados. Primeiro, foi desenvolvido um estudo para entender a propagação de mudanças na presença de dependência de características em várias linhas de produto industriais. Segundo, é proposto um arcabouço de medidas com o propósito de quantificar propriedades estruturais de dependências de características. Nesse contexto, também foi desenvolvido um estudo revelando que métricas convencionais tipicamente aplicadas em trabalhos de linha de produto, tais como a métrica de acoplamento, não são indicadores efetivos da propagação de mudanças em linhas de produto de software. As métricas propostas nesta tese superaram consistentemente as métricas convencionais estudadas. Terceiro, esta tese propõe um método para auxiliar a propagação de mudanças encarando informações sobre a organização de dependência de características encarando-as como um problema de agrupamento. Foi avaliado se a organização de informações proposta nesta tese tem potencial para auxiliar desenvolvedores a propagar mudanças em linhas de produto de software. / [en] Features are the key abstraction to develop and maintain software product lines. A challenge faced in the maintenance of product lines is the understanding of the dependencies that exist between features. In the source code, a feature dependency occurs whenever program elements within the boundaries of a feature s implementation depend on elements external to that feature. Examples are either attributes or methods defined in the realisation of a feature, but used in the code realising other features. As developers modify the source code associated with a feature, they must ensure that other features are consistently updated with the new changes – the so-called change propagation. However, appropriate change propagation is far from being trivial as features are often not modularised in the source code. In this way, given a change in a certain feature, it is challenging to reveal which (part of) other features should also change. Change propagation becomes, therefore, a central and non-trivial aspect of software product-line maintenance. Developers may overlook important parts of the code that should be revised or changed, thus not fully propagating changes. Conversely, they may also unnecessarily analyse parts that are not relevant to the feature-maintenance task at hand, thereby increasing the maintenance effort or even mis-propagating changes. The creation of a good mental model based on the structure of feature dependencies becomes essential for gaining insight into the intricate relationship between features in order to properly propagate changes. Unfortunately, there is no understanding in the state of the art about structural properties of feature dependencies that affect change propagation. This understanding is not yet possible as: (i) there is no conceptual characterisation and quantification means for structural properties of feature dependency, and (ii) there is no empirical investigation on the influence of these properties on change propagation. In this context, this thesis presents three contributions to overcome the aforementioned problems. First, we develop a study to understand change propagation in presence of feature dependencies in several industry-strength product lines. Second, we propose a measurement framework intended to quantify structural properties of feature dependencies. We also develop a study revealing that conventional metrics typically used in previous research, such as coupling metrics, are not effective indicators of change propagation in software product lines. Our proposed metrics consistently outperformed conventional metrics. Third, we also propose a method to support change propagation by facing the organisation of feature dependency information as a clustering problem. We evaluate if our proposed organisation has potential to help developers to propagate changes in software product lines.

In recent years, there has been a surge in research on theimpact of architectural smells on software maintainability.Maintainability in turn encompasses several other qualityattributes as sub-characteristics, such as modularity andtestability. However, the empirical evidence establishing aclear relationship between these quality attributes andarchitectural smells has been lacking. This study aims to fillthis gap by examining the correlation between sevenarchitectural smells and testability/modularity across 378versions of eight open-source projects. A self-developedtool—ASAT—was used to collect data on architecturalsmells and metrics relating to modularity and testability. Thecollected data was analyzed to reveal correlations at both theproject-level and within packages. Contrary to expectations,the findings show that, generally, there is no negativecorrelation between smells and modularity at the projectlevel, except for the Dense Structure smell. Remarkably,project-level testability showed the opposite result.However, a rival explanation proposes that the increasingsize of a project may be a stronger factor in this relationship.Similarly, package-level smells, as a whole, did not exhibit anegative correlation with testability. However, most smellsdemonstrated a stronger negative relationship with thequality attributes they were claimed to impair, incomparison to their counterparts. This empirical evidencesubstantiates the assertion that specific architectural smellsindeed relate to distinct quality attributes, which hadpreviously only been supported by argument.

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