Promoting Modularity in a Requirements Engineering Process for Software Product Lines

A Software Product Line (SPL) is a set of systems that share a group of manageable features and satisfy the specific needs of a particular domain. The features of an SPL can be used in variable combinations to derive product variants in the SPL domain. Because SPLs promote product development through reuse, it is vital to have a means to measure their quality in terms of quality attributes like complexity, reusability,… In this paper, we propose a set of metrics to evaluate the quality of an SPL at three levels: the feature model, design and code. We adapted a set of metrics for software quality and defined new metrics to deal with the inherent characteristics of SPLs, specifically the feature model and the traceability between features, design and code. Furthermore, to assist in interpreting the quality of a given SPL, we conducted an empirical study over ten open source SPLs to identify thresholds for the proposed metrics.

Software product line (SPL) is a software engineering paradigm for software development. A software product within a product line often has specific functionalities that are not common to all other products within the product line. Those specific functionalities are termed “variant features” in a product line. SPL paradigm involves the modeling of variant features. However, little work in SPL investigates and addresses the modeling of variant features specific to user interface (UI). Unified Modeling Language (UML) is the de facto modeling language for object-oriented software systems. It is known that UML needs better support in modeling UIs. Thus, much research developed UML extensions to improve UML support in modeling UIs. Yet little of this work is related to developing such extensions for modeling UIs for SPLs in which variant features specific to UI modeling must be addressed. This research develops a UML extension -Web User Interface Modeling Language (WUIML) to address these problems. WUIML defines elements for modeling variant features specific to user interfaces for Web-based SPLs. The model elements in WUIML extend from the metaclass and BasicActivity of the UML2.0 metamodel. WUIML integrates the modeling of variant features specific to user interfaces to UML. For example, in a Web-based patient registration software product line, member products targeting British users may use British date format in the user interface, while member products targeting United States users may use United States date format in the user interface. Thus, this is a variant feature for this product line. WUIML defines a model element, XOR, to represent such exclusive or conditions in a product line user interface model. WUIML would reduce SPL engineers’ efforts needed in UI development. To validate the WUIML research outcome, a case study was conducted. The results of this empirical study indicate that modeling UIs for Web-based SPLs using WUIML is more effective and efficient than using standard UML.

Software product family or line is a software engineering paradigm that systematizes reuse. In software product line engineering, two phases are distinguished: domain engineering which is in charge of developing a common infrastructure and assets and application engineering which makes use of those assets to generate the products. One of the key aspects of product lines is variability and its management. However, the main focus has been on functional variability and quality variability in software product lines has not received so much attention by researchers. In a product line different members of the line may require different levels of a quality requirement, for instance they could differ in terms of their availability, security, reliability, etc. Due to this variability, quality evaluation in software product lines is much more complicated that in single-systems. One alternative is to evaluate all the products of a line but it is very expensive and ways of reducing evaluation efforts are necessary. In this direction, the paper presents a method for facilitating cost-effective quality evaluation of a product line taking into consideration variability on quality attributes.

Lately, the demand for mobile applications development has increased significantly mainly due to growth of use of mobile devices and the need to port existing web applications. To reduce development’s time and cost, Software Product Lines (SPLs) have also been used in the context of mobile applications. However, the existing SPLs do not worry about supporting the development of mobile applications corresponding to the existing Web applications, as it is desirable to have access to the information and main features of these applications in mobile devices. In face of this problem, this paper discusses the motivation and presents the evolution from a SPL in the e-Gov Web (e-Gov Web SPL) domain to a SPL in the mobile domain (e-Gov Mobile SPL) having in mind the need to supply market demand. The conducted evolution was supported by the PLUS approach (Product Line UML-Based Software Engineering) and by the features model. Furthermore, this work debates the main results obtained through some e-Gov Mobile SPL instantiations in the precision livestock domain.KeywordsSoftware Product LineEvolutione-GovWebMobile

Needs for mass customization and economies of scale have pushed engineers to develop Software Product Lines (SPLs). SPLs are families of products sharing commonalities and exhibiting differences, built by reusing software assets abstractly represented by features. Feature models describe the constraints that link the features and allow the configuration of tailored software products. Common SPLs involve hundreds, even thousands of features, leading to billions of possible software products. As a result, testing a product line is challenging due to the enormous size of the possible products. Existing techniques focus on testing based on the product line's feature model by selecting a limited set of products to test. Being created manually or reverse-engineered, feature models are prone to errors impacting the generated test suites. In this paper, we examine ability of test suites to detect such errors. In particular, we propose two mutation operators to derive erroneous feature models (mutants) from an original feature model and assess the capability of the generated original test suite to kill the mutants. Experimentation on real feature models demonstrate that dissimilar tests suites have a higher mutant detection ability than similar ones, thus validating the relevance of similarity-driven product line testing.

A software product line (SPL) usually involves a shared set of core assets and a series of application products. To ensure consistency, the evolution of the core assets and all the application products should be coordinated and synchronized under a unified evolution process. Therefore, SPL evolution often involves cross-product propagation and synchronization besides application derivation based on core assets, presenting quite different characteristic from the evolution of individual software products. As software architectures, including the product line architecture (PLA) and application architectures, play a central role in SPL engineering and evolution, architecture-based evolution analysis is a natural way for analyzing and managing SPL evolution. In this paper, we explore common practices of architecture evolution and the rationale behind in industrial SPL development. To this end, we conduct a case study with Wingsoft examination system product line (WES-PL), an industrial product line with an evolution history of eight years and more than 10 application products. In the case study, we reviewed the evolution history of WES-PL architecture and analyzed several typical evolution cases. Based on the historical analysis, we identify some special problems in industrial SPL practice from the aspect of architecture evolution and summarize some useful experiences about SPL evolution decisions to complement classical SPL methodology. On the other hand, we also propose some possible improvements for the evolution management in WES-PL.

Automated diagnosis of feature model configurations

Software product lines are able to describe multiple products sharing a common base of features and are commonly described as feature models. For complex software product lines, automatic analyses are required to ensure validity and to improve the interactive configuration process. Modern SAT solvers are vital components for the validation process of feature models. The increasing variability of software product lines implies the need to use more expressive solvers like SMT solvers. To assist the development of feature modeling tools, we compare SAT and SMT solvers for the automated analysis of feature models. During this thesis, we create an abstract data type to formally define analyses for feature model defects and their explanations. The result shows that SAT solvers are more efficient at detecting the defects, while SMT solvers can find explanations for them multiple times faster. Feature models can be further expanded by attaching attributes to features. Such attributes may contain a numerical value. Additionally, one attribute can be defined for multiple features. In this thesis, we aim to support the interactive configuration process, by providing the range of the sum of values for an attribute. Such ranges depend on the remaining choices in a configuration of the product line. We provide an exact computation using SMT and an approximation using a heuristic. The evaluation results show that an SMT solver is not suitable for supporting interactive configuration. However, the approximated ranges of the provided heuristic were very close to the exact ones.

Automating feature model refactoring: A Model transformation approach

With the growing academic and industrial interest in Software Product Lines, one area demanding special attention is tool support development, which is a pre-requisite for widespread software product lines practices adoption. In this demo, we present FLiP, a suite of tools consisting of 3 modules: a refactoring tool that implements code transformations for extracting product variations from Java classes into AspectJ aspects, a module that integrates with a Feature Model tool for updating a software product lines feature model accordingly to code transformations, and a tool responsible for building the final products. FLiP has been designed and tested in the context of industrial-strength mobile game software product lines.

With rapid development of software product line research, how to manage reusable resources is becoming increasingly important. The description and organization of resources are key techniques for a resource repository. We present an XML based interface specification to formalize the description of resources. And we organize resources with a feature model which is proved to be an effective way to manage commonalities and variations in software product line. The model proposed can be applied to various resource scenarios and is easier to query and interoperate. In studying the data processing domain, we build a resource repository and a corresponding managing tool to categorize and query resources from the software product line.

BackgroundThe software product lines (SPL) enable development teams to fully address a systematic reuse of shared assets to deliver a family of similar software products. Mobile applications are an obvious candidate for employing an SPL approach. This paper presents our research outcomes, based on empirical data from an industry-level development project. Two development teams were confronted with the same functionalities set to be delivered through a family of native mobile applications for Android and iOS.MethodsEmpirical data was gathered before, during and after a year of full-time development. The data demonstrate the impact of a SPL approach by comparing the SPL and non-SPL multiple edition development. One family of products (Android apps) was developed using an SPL approach, while another (iOS apps), functionally the same, was developed without employing an SPL approach. The project generated a volume of raw and aggregated empirical data to support our research questions.ResultsThe paper reports a positive impact of an SPL approach on product quality (internal and external) and feature output per week. As data shows, it also increases the delivery of functionalities (240% in 6 more editions), while investing the same amount of effort needed for a single-edition development. As a result of system-supported separation of development and production code, developers had a high confidence in further development. On the other hand, the second team delivered less new functionalities, only two new application editions, and lower software quality than the team that manages multi-edition development by employing an SPL approach.

At the heart of product line development is the assumption that through structured reuse later products will be of a higher quality and require less time and effort to develop and test. This thesis presents empirical results from two case studies aimed at assessing the quality aspect of this claim and exploring fault prediction in the context of software product lines. The first case study examines pre-release faults and change proneness of four products in PolyFlow, a medium-sized, industrial software product line; the second case study analyzes post-release faults using pre-release data over seven releases of four products in Eclipse, a very large, open source software product line.;The goals of our research are (1) to determine the association between various software metrics, as well as their correlation with the number of faults at the component/package level; (2) to characterize the fault and change proneness of components/packages at various levels of reuse; (3) to explore the benefits of the structured reuse found in software product lines; and (4) to evaluate the effectiveness of predictive models, built on a variety of products in a software product line, to make accurate predictions of pre-release software faults (in the case of PolyFlow) and post-release software faults (in the case of Eclipse).;The research results of both studies confirm, in a software product line setting, the findings of others that faults (both pre- and post-release) are more highly correlated to change metrics than to static code metrics, and are mostly contained in a small set of components/ packages. The longitudinal aspect of our research indicates that new products do benefit from the development and testing of previous products. The results also indicate that pre-existing components/packages, including the common components/packages, undergo continuous change, but tend to sustain low fault densities. However, this is not always true for newly developed components/packages. Finally, the results also show that predictions of pre-release faults in the case of PolyFlow and post-release faults in the case of Eclipse can be done accurately from pre-release data, and furthermore, that these predictions benefit from information about additional products in the software product lines.

Software Product Lines (SPL) adoption can affect several aspects of an organization and it involves significant investment and risk. This way, SPL risk management is a crucial activity of SPL adoption. This study aims to identify SPL risks during the scoping and requirement disciplines to provide information to better understand risk management in SPL. In order to achieve the previous stated goal, a case study research was applied in an industrial project in the medical information management domain. Using the captured risks, a classification scheme was built and risk mitigation strategies were identified. We spent five months, totaling 79 hours, performing risk management (RM) in the scoping discipline and twelve months, totaling 148 hours, performing RM on the requirements discipline. We identified 32 risks during the scoping discipline and 20 risks during the requirements discipline, 14 risks occurred in both disciplines. Some identified risks are not particular to SPL development, however, they have their impact increased due to the SPL characteristic. All the study results and lessons learned are useful for all project managers and researchers who are considering the introduction of SPL risk management in industry or academia.

Software Product Line Engineering aims to ensure the correctness, completeness and consistency among its artifacts and the specified domain, in order to prevent the spread of defects for the products derived from this domain. Among initial artifacts of a software product line, feature models are artifacts generated in various domain engineering approaches. Although software inspection is highlighted as an effective review activity for detection of defects in software artifacts, mainly in the early models of software projects, a recent quasi-systematic review of literature indicated a lack of techniques to support the inspection of software product line artifacts, which include features models. Thus, this paper presents FMCheck, a checklist-based inspection technique to support the detection of defects on feature models. This technique was developed to be configurable and to be applied on several extensions of the original feature model notation presented by FODA approach, including the Odyssey-FEX notation, in particular. FMCheck was submitted to a proof of concept and to a further in vitro feasibility study, in which it could be seen the feasibility of FMCheck application and also that inspections applying FMCheck are more effective than ad-hoc inspections, when applied on four distinct domains.