Anders Wesslén

Improving the use case driven approach to requirements engineering

The paper presents the idea of usage oriented requirements engineering, an extension of use case driven analysis. The main objective is to achieve a requirements engineering process resulting in a model which captures both functional requirements and system usage aspects in a comprehensive manner. The paper presents the basic concepts and the process of usage oriented requirements engineering, and the synthesized usage model resulting from this process. The role of this model in system development, and its potential applications are also discussed.

The importance of quality requirements in software platform development-a survey

This paper presents a survey where some quality requirements that commonly affect software architecture have been prioritized with respect to cost and lead-time impact when developing software platforms and when using them. Software platforms are the basis for a product-line, i.e. a collection of functionality that a number of products is based on. The survey has been carried out in two large software development organizations using 34 senior participants. The prioritization was carried out using the Incomplete Pairwise Comparison method (IPC). The analysis shows that there are large differences between the importance of the quality requirements studied. The differences between the views of different stakeholders are also analysed and it is found to be less than the difference between the quality requirements. Yet this is identified as a potential source of negative impact on product development cost and lead-time, and rules of thumb for reducing the impact are given.

A Replicated Empirical Study of the Impact of the Methodsin the PSP on Individual Engineers

The Personal Software Process (PSP) has during the last couple ofyears gained attention as a way to individual improvements insoftware development. The PSP is introduced to students and engineersthrough a course, which introduces a personal software developmentprocess. The personal software development process is improvedin steps during the course and a collection of methods is introducedto support the personal development process. The question is,however, how do these methods influence the performance of anindividual engineer? This question has been studied in a studymade at the Software Engineering Institute, and the study hasshown that the methods in the PSP have a positive effect on theperformance of the individuals. There is however a need to replicatethis study to confirm the findings in other settings and withother individuals.This paper describes a replicationof the study made at the Software Engineering Institute. Boththe original study and this replication are made on data reportedfrom the students taking the PSP course. The differences betweenthe two studies are the programming languages used, which heldthe courses, the class sizes, and the experiences of the students.In summary, the results from this replication confirm the resultsin the original study: Size estimation accuracy gets better,the defect density gets lower, the defects are found earlierand that the pre-compile yield gets better during the PSP course.Basically, the two studies show that the methods in the PSP helpengineers to improve their performance.

Understanding software defect detection in the Personal Software Process

There is a general need to understand software defects and the ability to detect defects during different activities. This is particularly important in relation to software process improvement, where one objective may be to decrease the number of defects. The Personal Software Process (PSP) has gained attention during the last couple of years as a way to individual improvement in software development. Thus, the PSP is an interesting starting point to understand software defects and in particular the detection process. The paper presents a study of software defect detection for 59 students taking a PSP course. In summary, the study provides valuable insight into software defect detection in the PSP. Some of the results are interesting not only for the PSP, but from a general perspective in the understanding of software defect detection. The understanding of software defects forms the basis for improving the reliability of software.

Assessing the sensitivity to usage profile changes in test planning

Software reliability is an important characteristic for most systems, but due to its dynamic properties it is hard to assess until very late in the development. Nevertheless, the testing must be planned to meet the reliability requirements. In test planning, the notion of usage coverage may be used as an indicator of reliability as they are correlated with each other. When the testing is planned, the test cases to be run and the usage profile are derived. The usage profile is estimated using the available information of the expected usage. There are therefore some uncertainties in the estimated usage profile. The paper presents and evaluates a method for analysing the impact of uncertainties in the usage profile on the usage coverage. The method is applied during test planning to evaluate how sensitive the usage coverage is to usage profile uncertainties. Different usage profiles are simulated using the expected usage profile and an uncertainty expressed as a percentage value or a range within which the changed usage profile may vary. Test cases are derived from the expected usage profile and the resulting usage coverage is estimated for each simulated usage profile. Thus the impact in the usage coverage can be analysed. The presented analysis method is illustrated with an example system. One of the conclusions from this first study of the method is that the sparseness of the usage profile, which is defined by limitations in the usage pattern, reduces the impact of the usage profile uncertainties. Further, the number of test cases is an important factor in the sensitivity to uncertainties in the usage profile.

Statistical Usage Testing Using SDL

Statistical Usage Testing is a scientific approach to software testing. Instead of ad hoc selection of test cases, the selection is controlled by a usage specification which models the anticipated software usage and hence not the system itself. The test cases are derived from the usage specification and constitute a sample from the operational usage. Thus the software reliability can be certified by applying a statistical model.

Systematic Literature Reviews

Systematic literature reviews are conducted to “identify, analyse and interpret all available evidence related to a specific research question” [96]. As it aims to give a complete, comprehensive and valid picture of the existing evidence, both the identification, analysis and interpretation must be conducted in a scientifically and rigorous way. In order to achieve this goal, Kitchenham and Charters have adapted guidelines for systematic literature reviews, primarily from medicine, evaluated them [24] and updated them accordingly [96]. These guidelines, structured according to a three-step process for planning, conducting and reporting the review, are summarized below.

Early Estimation of Software Reliability through Dynamic Analysis

Early estimations and predictions of software quality attributes are essential to be in control of software development and to allow for delivery of software products which fulfil the requirements put on them. This paper focuses on a method enabling estimation and prediction of software reliability from the specification and design documents. The method is based on dynamic analysis of a well-defined high level description technique, and by applying usage-oriented analysis, it is illustrated, through a case study, how the reliability can be controlled. Furthermore, it is described how the output from the analysis can be used as an acceptance criterion of the design, as support in the planning process for the test phases to come and finally as a method to enable estimation and prediction of the reliability in the testing phase and operational phase. The method is still being evaluated and improved, but it can be concluded that so far the results are inspiring for the future.

Software Reliability Estimations through Usage Analysis of Specifications and Designs

This paper presents a method proposal for estimation of software reliability before the implementation phase. The method is based upon that a formal specification technique is used and that it is possible to develop a tool performing dynamic analysis, i.e., locating semantic faults in the design. The analysis is performed with both applying a usage profile as input as well as doing a full analysis, i.e., locate all faults that the tool can find. The tool must provide failure data in terms of time since the last failure was detected. The mapping of the dynamic failures to the failures encountered during statistical usage testing and operation is discussed. The method can be applied either on the software specification or as a step in the development process by applying it on the software design. The proposed method allows for software reliability estimations that can be used both as a quality indicator, and for planning and controlling resources, development times, etc. at an early stage in the development of software systems.

Presentation and Package

When an experiment is completed, the findings may be presented for different audiences, as defined in Fig. 11.1. This could, for example, be done in a paper for a conference or a journal, a report for decision-makers, a package for replication of the experiment, or as educational material. The packaging could also be done within companies to improve and understand different processes. In this case, it is appropriate to store the experiences in an experience base according to the concepts discussed by Basili et al. [16].