Software reuse is perceived as the key to successful software development because of the potential for shortened time to market, increased quality and reduced costs. In recent years software product lines have emerged as a promising way to achieve large scale software reuse. Challenges against successful reuse when developing in a software product line involves management of the differences between products, and the differences between different releases of the products. In this thesis we present the experiences from a series of case studies within four software companies. Based on these we present a taxonomy of the technical solutions to manage product differences, a historical essay of how components in a software product line can evolve and what mechanisms that are used to support this evolution. From this we elaborate on the connection between evolution and variability, i.e. the ability of the software architecture and components to support the differences between products. We argue that evolution is strongly connected to variability, and that by foreseeing the evolution, the software can be instrumented with appropriate variability mechanisms accordingly. Moreover, we argue that some types of evolution are more frequent than others, and that the efforts should mainly go in the direction of foreseeing and instrumenting for these types of evolution.

No description available.

No description available.

Programmers are encouraged to comment their source programs, yet the value of the comments is not easily verified. In this study, the relationships between comment quantity and software metrics are assessed to determine whether programmers increase comment quantity in complex modules. In addition, comment quantity and software metrics are related to software maintenance data. It was found that software complexity, as measured by software metrics, accounts for a substantial portion of the variance in comment quantity. Additionally, comment quantity has no statistically significant relationship to software maintainability for the task studied. / Master of Science

A model of the software evolution process, called the Abstraction Refinement Model, is described which builds on the algebraic influence of the Laws of Programming and the transformational Draco Paradigm. The result is an algebraic structure consisting of the states of the software product (system descriptions) ordered by a relation of relative correctness with transformations defined between the system descriptions. This structure is interpreted as the software evolution space, with the intended semantics given by a model combining axiomatic semantics and the Lindenbaum algebra of a first-order logic. Using this interpretation, software evolution can be represented as a sequence of transformations on system descriptions. The primary contributions of the characterization of software evolution are to the understanding of maintenance and its relationship to development. The influence of development on maintenance is shown as the transfer of a "descriptive context" for the software system. This context is used as an information source during maintenance, and is progressively modified by maintenance activities. These activities are characterized by balanced forward and reverse transformations. The use of reverse transformations explaining the role of reverse engineering in maintenance for information gathering and document reconstruction. Additionally, the form of maintenance affects the performance of the activity, with adaptive maintenance differing from corrective, perfective and preventive maintenance. These factors contribute to the descriptive nature and utility of the Abstraction Refinement Model in defining methodologies for maintenance. / Master of Science

This thesis describes the results of a research effort focusing on the validation of a procedure for assessing the quality of an Ada-based product. Starting with the identification of crucial Ada constructs, this thesis outlines a seven step process for defining metrics that support software quality assessment within a framework based on linkages among software engineering objectives, principles, and attributes. The thesis presents the impact of the use of crucial Ada constructs on the software engineering attributes and describes measurement approaches for assessing that impact This thesis also outlines a planned research effon to develop an automated analyzer for the assessment of software quality in Ada-based products and plans for validating the assessment procedure. / Master of Science

For many years the software engineering community has been attacking the software reliability problem on two fronts. First via design methodologies, languages and tools as a precheck on quality and second by measuring the quality of produced software as a postcheck. This research attempts to unify the approach to creating reliable software by providing the ability to measure the quality of a design prior to its implementation. Also presented is a comparison of a graphical and a textual design language in an effort to support cognitive science research findings that the human brain works more effectively in images than in text. / Master of Science

Maintenance of software makes up a large fraction of the time and money spent in the software life cycle. By reducing the need for maintenance these costs can also be reduced. Predicting where maintenance is likely to occur can, help to reduce maintenance by prevention. This thesis details a study of the use of software quality;metrics to determine high complexity components in a software system. By the use of a history of maintenance done on a particular system, it is shown that a predictor equation can be developed to identify components which needed maintenance activities. This same equation can also be used to determine which components are likely to need maintenance in the future. Through the use of.these predictions and software metric complexities it should be possible to reduce the likelihood of a component needing maintenance. This might be accomplished by reducing the complexity of that component through further decomposition. / Master of Science

New software tools and methodologies make claims that managers often believe intuitively without evidence. Many unsupported claims have been made about object-oriented programming. However, without rigorous scientific evidence, it is impossible to accept these claims as valid. Although experimentation has been done in the past, most of the research is very recent and the most relevant research has serious drawbacks. This study attempts to empirically verify the claim that object-oriented languages produce programs that are more easily maintained than those programmed with procedural languages. Measurements of subjects performing maintenance tasks onto two identical programs, one object-oriented and the other procedure-oriented show the object-oriented version to be more maintainable. / Master of Science

<p>Att sätta sig in i system kan vara krångligt utan rätt sorts dokumentation. Vi har undersökt vilken dokumentation som kan vara lämplig att lämna över till nya utvecklare, som ska arbeta vidare med systemet i software maintenance fasen.</p><p>Det har gjorts genom att vi har gjort en litteraturstudie om dokumentation samt undersökt vad för dokumentationsartefakter som används när man ska sätta sig in i datorsystem. Vi använde eXtreme Programming för att utveckla ett system som vi försökte dokumentera samtidigt som vi utvecklade det.</p><p>eXtreme Programming förordar muntlig kommunikation, vilket är svårt att lämna över till nya utvecklare. Vi upptäckte under vår utveckling att det var svårt att föra in dokumentation sam-tidigt som utvecklandet pågick,  därför använde vi bara enhetstester och  strukturerade kod-kommentarer under utvecklingsiterationerna.</p><p>Vi undersökte hur dokumentationen som skapats fungerade genom att göra en undersökning bestående av strukturerade intervjuer där de fick komma med kommentarer om hur dokumen-tationen hjälpte förståelsen för systemet.</p><p>Vi lämnar ifrån oss en vidareutveckling  av eXtreme Programming  som innefattar en doku-mentationsiteration  innan överlämnandet  samt en studie om vad för dokumentation som är värdefull att ha vid systemöverlämningar.</p> / <p>Understanding systems can be a tough task without the right sort of documentation. We have examined the documentation artifacts which may be appropriate to hand over to new develop-ers, who will continue working with the system during the software maintenance phase.</p><p>By doing a literature review on documentation and examined what documentation artifacts is used when you want to  understand a computer system. We used the eXtreme Programming system development methodology to develop a system that we tried to document as we devel-oped it.</p><p>eXtreme Programming favors oral communication, but that is hard to hand over to new devel-opers. We discovered during our development that it was difficult to introduce documentation while the development process was going on so we only used structured code comments and unit testing during the development iterations</p><p>We examined how the documentation that was created worked by doing a survey consisting of structured interviews where the respondents made comments about if and how the documen-tation improved their understanding of the system.</p><p>We pass on an evolved eXtreme Programming system development methodology, which in-cludes a standalone documentation iteration before the handover, and a study of what kind of documentation that is valuable to have when transferring systems to new developers.</p>