Arnaud Hubaux

Generating range fixes for software configuration

To prevent ill-formed configurations, highly configurable software often allows defining constraints over the available options. As these constraints can be complex, fixing a configuration that violates one or more constraints can be challenging. Although several fix-generation approaches exist, their applicability is limited because (1) they typically generate only one fix, failing to cover the solution that the user wants; and (2) they do not fully support non-Boolean constraints, which contain arithmetic, inequality, and string operators. This paper proposes a novel concept, range fix, for software configuration. A range fix specifies the options to change and the ranges of values for these options. We also design an algorithm that automatically generates range fixes for a violated constraint. We have evaluated our approach with three different strategies for handling constraint interactions, on data from five open source projects. Our evaluation shows that, even with the most complex strategy, our approach generates complete fix lists that are mostly short and concise, in a fraction of a second.

Supporting multiple perspectives in feature-based configuration

Feature diagrams have become commonplace in software product line engineering as a means to document variability early in the life cycle. Over the years, their application has also been extended to assist stakeholders in the configuration of software products. However, existing feature-based configuration techniques offer little support for tailoring configuration views to the profiles of the various stakeholders. In this paper, we propose a lightweight, yet formal and flexible, mechanism to leverage multidimensional separation of concerns in feature-based configuration. We propose a technique to specify concerns in feature diagrams and to generate automatically concern-specific configuration views. Three alternative visualisations are proposed. Our contributions are motivated and illustrated through excerpts from a real web-based meeting management application which was also used for a preliminary evaluation. We also report on the progress made in the development of a tool supporting multi-view feature-based configuration.

Towards Multi-view Feature-Based Configuration

[Context & motivation] Variability models, feature diagrams ahead, have become commonplace in software product line engineering as a means to document variability early in the lifecycle. Over the years though, their application span has been extended to aid stakeholders in the configuration of software products. [Question/problem] However, current feature-based configuration techniques hardly support the tailoring of configuration views to the profiles of heterogeneous stakeholders. [Principal ideas/results] In this paper, we introduce a lightweight mechanism to leverage multidimensional separation of concerns in feature-based configuration. [Contribution] We propose a technique to specify concerns in feature diagrams and to build automatically concern-specific configuration views, which come with three alternative visualisations.

A user survey of configuration challenges in Linux and eCos

Operating systems expose sophisticated configurability to handle variability in hardware platforms like mobile devices, desktops, and servers. The variability model of an operating system kernel like Linux contains thousands of options guarded by hundreds of complex constraints. To guide users throughout the configuration and ensure the validity of their decisions, specialized tools known as configurators have been developed. Despite these tools, configuration still remains a difficult and challenging process. To better understand the challenges faced by users during configuration, we conducted two surveys, one among Linux users and another among eCos users. This paper presents the results of the surveys along three dimensions: configuration practice; user guidance; and language expressiveness. We hope that these results will help researchers and tool builders focus their efforts to improve tool support for software configuration.

Separation of concerns in feature diagram languages: A systematic survey

The need for flexible customization of large feature-rich software systems, according to requirements of various stakeholders, has become an important problem in software development. Among the many software engineering approaches dealing with variability management, the notion of Software Product Line (SPL) has emerged as a major unifying concept. Drawing from established disciplines of manufacturing, SPL approaches aim to design repertoires of software artifacts, from which customized software systems for specific stakeholder requirements can be developed. A major difficulty SPL approaches attempt to address is the modularization of software artifacts, which reconciles the users needs for certain features and the development and technical constraints. Towards this end, many SPL approaches use feature diagrams to describe possible configurations of a feature set. There have been several proposals for feature diagram languages with varying degrees of expressiveness, intuitiveness, and precision. However, these feature diagram languages have limited scalability when applied to realistic software systems. This article provides a systematic survey of various concerns of feature diagrams and ways in which concerns have been separated. The survey shows how the uncertainty in the purpose of feature diagram languages creates both conceptual and practical limitations to scalability of those languages.

Evaluating a textual feature modelling language: four industrial case studies

Feature models are commonly used in software product line engineering as a means to document variability. Since their introduction, feature models have been extended and formalised in various ways. The majority of these extensions are variants of the original tree-based graphical notation. But over time, textual dialects have also been proposed. The textual variability language (TVL) was proposed to combine the advantages of both graphical and textual notations. However, its benefits and limitations have not been empirically evaluated up to now. In this paper, we evaluate TVL with four cases from companies of different sizes and application domains. The study shows that practitioners can benefit from TVL. The participants appreciated the notation, the advantages of a textual language and considered the learning curve to be gentle. The study also reveals some limitations of the current version of TVL.

Variability Modeling Challenges from the Trenches of an Open Source Product Line Re-engineering Project

Variability models, feature diagrams ahead, have become commonplace in the software product lines engineering literature. Whereas ongoing research keeps improving their expressiveness, formalisation and automation, more experience reports on their usage in real projects are needed. This paper describes some challenges encountered during the re-engineering of PloneMeeting, an Open Source software family, into a software product line. The main challenging issues we could observe were (i) the ambiguity originating from implicit information (missing definitions of feature labels and unclear modelling viewpoint), (ii) the necessity of representing spurious features, (iii) the difficulty of making diagrams and constraints resistant to change, and (iv) the risks of using feature attributes to represent large sets of subfeatures. Our study reveals the limitations of current constructs, and calls for both language and methodological improvements. It also suggests further comparative evaluations of modelling alternatives.

Towards more reliable configurators: a re-engineering perspective

Delivering configurable solutions, that is products tailored to the requirements of a particular customer, is a priority of most B2B and B2C markets. These markets now heavily rely on interactive configurators that help customers build complete and correct products. Reliability is thus a critical requirement for configurators. Yet, our experience in industry reveals that many configurators are developed in an ad hoc manner, raising correctness and maintenance issues. In this paper, we present a vision to re-engineering more reliable configurators and the challenges it poses. The first challenge is to reverse engineer from an existing configurator the variability information, including complex rules, and to consolidate it in a variability model, namely a feature model. The second challenge is to forward engineer a new configurator that uses the feature model to generate a customized graphical user interface and the underlying reasoning engine.

Separating variability concerns in a product line re-engineering project

Feature diagrams have now become common variability models in software product lines engineering literature. Whereas ongoing research keeps improving their expressiveness, formalisation, and automation, open studies of their usage in real projects are still missing. This paper intends to (1) present the process we followed to elicit the variability of PloneMeeting, an Open Source project, and (2) report on the initial results obtained when applying variability modelling techniques promoting separation of concerns between software variability and product line variability.

Separating Concerns in Feature Models: Retrospective and Support for Multi-Views

Feature models (FMs) are a popular formalism to describe the commonality and variability of a set of assets in a software product line (SPL). SPLs usually involve large and complex FMs that describe thousands of features whose legal combinations are governed by many and often complex rules. The size and complexity of these models is partly explained by the large number of concerns considered by SPL practitioners when managing and configuring FMs. In this chapter, we first survey concerns and their separation in FMs, highlighting the need for more modular and scalable techniques. We then revisit the concept of view as a simplified representation of an FM. We finally describe a set of techniques to specify, visualise and verify the coverage of a set of views. These techniques are implemented in complementary tools providing practical support for feature-based configuration and large-scale management of FMs.