This paper presents NoFun, a notation aimed at dealing with non-functional aspects of software systems at the product level in the component programming framework. NoFun can be used to define hierarchies of non-functional attributes, which can be bound to individual software components, libraries of components or (sets of) software systems. Non-functional attributes can be defined in several ways, being possible to choose a particular definition in a concrete context. Also, NoFun allows to state the values of the attributes in component implementations, and to formulate non-functional requirements over component implementations. The notation is complemented with an algorithm able to select the best implementation of components (with respect to their non-functional characteristics) in their context of use. Key words: component programming, non-functional requirements. 1. Introduction 1.1. Motivation Software systems can be characterised both by their functionality (what the system do...

The quality of a design has a decisive impact on the quality of a software product; but due to the diversity and complexity of design properties (e.g., coupling, encapsulation), their assessment and correlation with external quality attributes (e.g., maintenance, portability) is hard. In contrast to traditional quality models that express the “goodness ” of design in terms of a set of metrics, the novel Factor-Strategy model proposed by this paper, relates explicitly the quality of a design to its conformance with a set of essential principles, rules and heuristics. This model is based on a novel mechanism, called detection strategy, that raises the abstraction level in dealing with metrics, by allowing to formulate good-design rules and heuristics in a quantifiable manner, and to detect automatically deviations from these rules. This quality model provides a twofold advantage: (i) an easier construction and understanding of the model as quality is put in connection with design principles rather than “raw numbers”; and (ii) a direct identification of the real causes of quality flaws. We have validated the approach through a comparative analysis involving two versions of a industrial software system.

Due to its economic impact "maintainability" is broadly accepted as an important quality attribute of software systems. But in contrast to attributes such as performance and correctness, there is no common understanding of what maintainability actually is, how it can be achieved, measured, or assessed. In fact, every software organization of significant size seems to have its own definition of maintainability. We address this problem by defining an unique two-dimensional quality model that associates maintenance activities with system properties including the capabilities of the organization. The separation of activities and properties facilitates the identification of sound quality criteria and allows to reason about their interdependencies. The resulting quality controlling process enforces these criteria through toolsupported measurements as well as manual inspections. We report on our experiences with the incremental development of the quality model and its application to large scale commercial software projects. Among the positive effects are a slowdown of decay and a significantly increased awareness for long-term quality aspects.

Maintainability is a key quality attribute of successful software systems. However, its management in practice is still problematic. Currently, there is no comprehensive basis for assessing and improving the maintainability of software systems. Quality models have been proposed to solve this problem. Nevertheless, existing approaches do not explicitly take into account the maintenance activities, that largely determine the software maintenance effort. This paper proposes a 2-dimensional model of maintainability that explicitly associates system properties with the activities carried out during maintenance. The separation of activities and properties facilitates the identification of sound quality criteria and allows to reason about their interdependencies. This transforms the quality model into a structured and comprehensive quality knowledge base that is usable in industrial project environments. For example, review guidelines can be generated from it. The model is based on an explicit quality metamodel that supports its systematic construction and fosters preciseness as well as completeness. An industrial case study demonstrates the applicability of the model for the evaluation of the maintainability of Matlab Simulink models that are frequently used in modelbased development of embedded systems.

Usability is a key quality attribute of successful software systems. Unfortunately, there is no common understanding of the factors influencing usability and their interrelations. Hence, the lack of a comprehensive basis for designing, analyzing, and improving user interfaces. This paper proposes a 2dimensional model of usability that associates system properties with the activities carried out by the user. By separating activities and properties, sound quality criteria can be identified, thus facilitating statements concerning their interdependencies. This model is based on a tested quality meta-model that fosters preciseness and completeness. A case study demonstrates the manner by which such a model aids in revealing contradictions and omissions in existing usability standards. Furthermore, the model serves as a central and structured knowledge base for the entire quality assurance process, e.g. the automatic generation of guideline documents.

Professional programmers need common coding conventions to assure co-operation and a degree of quality of the software. Novice programmers, however, easily forget issues of programming style in their programming coursework. In particular with large classes, students may pass several courses without learning elements of programming style. This is often due to shortage of tutor work to give students thorough feedback on their coursework. Incorporating issues of style into programming courses is too often neglected and students are hoped to learn these issues by themselves. To deal with the problem, a set of coding rules was collected and justified to be used in C++ programming courses of the university. An automatic C++ programming style analyzer tool was implemented to ensure that students were following the rules. Students can freely use this tool to improve the quality of their coursework, and tutors can use it for assessing the assignments. Assessment rules and criteria can be easily adjusted according to the needs of the course or the exercise in question. Since basic programming style issues are assessed by the students independently before coursework submission, the teaching staff can concentrate on giving feedback on the more advanced features of program design and course specific issues. The approach seems to have tackled the basic problem well. The students learn to pay better attention

This paper presents a Quality Factor (QF) for software to give quality a value, relevant for all three viewpoints considered. QF uses an open weight scale methodology, to let you use the preferred measurement scale. Since the fundamental relevance to permit the adoption of a common IT language and to have an external comparability of your own internal results, ISO/IEC 9126 standard (12) was chosen as a basis to build the tools for QF calculation

Abstract — In today's embedded software systems development, non-functional requirements (e.g., dependability, maintainability) are becoming more and more important. Simultaneously the increasing pressure to develop software in less time and at lower costs pushes software industry towards product line’s solutions. To support product lines for high quality embedded software, quality models are needed. In this paper, we investigate to which extent existing quality modeling approaches facilitate high quality software product lines. First, we define several requirements for an appropriate quality model. Then, we use those requirements to review the existing quality modeling approaches. We conclude from the review that no single quality model fulfills all of our requirements. However, several approaches contain valuable characteristics. Based upon those characteristics, we propose the Prometheus approach. Prometheus is a goal-oriented method that integrates quantitative and qualitative approaches to quality control. The method starts quality modeling early in the software lifecycle and is reusable across product lines.

The differences between software quality and information systems quality are discussed from three different viewpoints - managerial, organisational, and engineering. The objective is to highlight the true meaning of information systems quality (ISQ) by considering its role in organisations and by comparing it with software quality (SWQ). An understanding of the relationship between software quality and information systems and their mutual influences is expected to help develop quality improvement programs. The paper is based on interview material provided by three experienced researchers in the field of computing and information technology (IT), each representing his own perspective on information and software systems which reflect the background and current position in academia. The initial set of questions used in the research for this paper was formulated by the information systems research team lead by professor Trevor Wood-Harper from Salford University. The organisational viewpoi...

Software quality models are a well-accepted means to support quality management of software systems. Over the last 30 years, a multitude of quality models have been proposed and applied with varying degrees of success. Despite successes and standardisation efforts, quality models are still being criticised, as their application in practice exhibits various problems. To some extent, this criticism is caused by an unclear definition of what quality models are and which purposes they serve. Beyond this, there is a lack of explicitly stated requirements for quality models with respect to their intended mode of application. To remedy this, this paper describes purposes and usage scenarios of quality models and, based on the literature and experiences from the authors, collects critique of existing models. From this, general requirements for quality models are derived. The requirements can be used to support the evaluation of existing quality models for a given context or to guide further quality model development.