Cardinality-Based Feature Models With Constraints: A Pragmatic Approach

International audienceFeature models originating from Software Product Line Engineering are a well-known approach to variability modeling. In many situations, the variability does not apply only on features but also on the number of times these features can be cloned. In such a case, cardinality-based feature models are used to specify the number of clones for a given feature. Although previous works already investigated approaches for feature modeling with cardinality, there is still a lack of support for constraints in the presence of clones. To overcome this limitation, we present an abstract model to define constraints in cardinality-based feature models and propose a formal semantics for this kind of constraints. We illustrate the practical usage of our approach with examples from our recent experiences on cloud computing platform configuration

Beyond Boolean product-line model checking: Dealing with feature attributes and multi-features

International audienceModel checking techniques for software product lines (SPL) are actively researched. A major limitation they currently have is the inability to deal efficiently with non-Boolean features and multi-features. An example of a non-Boolean feature is a numeric attribute such as maximum number of users which can take different numeric values across the range of SPL products. Multi-features are features that can appear several times in the same product, such as processing units which number is variable from one product to another and which can be configured independently. Both constructs are extensively used in practice but currently not supported by existing SPL model checking techniques. To overcome this limitation, we formally define a language that integrates these constructs with SPL behavioral specifications. We generalize SPL model checking algorithms correspondingly and evaluate their applicability. Our results show that the algorithms remain efficient despite the generalization

Handling Constraints in Cardinality-Based Feature Models: The Cloud Environment Case Study

Feature modeling is a well-known approach to describe variability in Software Product Lines. Cardinality-based Feature Models (FMs) is a type of FMs where features can be instantiated several times in the configuration, contrarily to boolean FMs where a feature is present or not. While boolean FMs configuration is easily handled by current approaches, there is still a lack of support regarding cardinality-based FMs. In particular, expressing constraints over the set of feature instances is not supported in current approaches, where cardinality involved in such constraints can not be specified. To face this limitation, we define in this paper cardinality-based expressions and provide the related formal syntax and semantics as well as the way to automate the underlying configuration. We study the need for such a support using cloud computing environment configurations as a motivating example. To evaluate the soundness of the proposed approach, we analyze a corpus of 10 cloud environments. Our empirical evaluation shows that constraints relying on our cardinality-based expressions are common and that our approach is effective and can provide an useful support to developers for modeling and reasoning about FMs with cardinalities.La modélisation à l'aide de caractéristiques est une approche très utilisée dans les lignes de produits logiciels. Les Modèles de Caractéristiques (MCs) étendus avec des cardinalités sont un des MCs dans lesquels une caractéristique peut être instanciée plusieurs fois lors de la configuration, contrairement au MCs booléens dans lesquels une caractéristique est présente ou non. Alors que la configuration de MCs booléens est aujourd'hui maitrisée par différentes approches, il reste cependant un manque en terme de support pour les MCs étendus avec des cardinalités. Notamment, pouvoir exprimé des contraintes sur le nombre d'instances requises n'est pas permis dans les approches existantes, puisque les contraintes ne peuvent être exprimées que sur des caractéristiques booléennes. Pour contrer cette limite, nous fournissons dans cet article une nouvelle notation pour exprimer ces contraintes, une définition formelle de leur syntaxe et de leur sémantique ainsi qu'un moyen d'automatiser la vérification des configurations associées. Pour illustrer notre approche, nous étudions le besoin pour un tel support dans le cadre de la configuration d'environnements d'informatique dans les nuages. Nous évaluons notre approche sur un ensemble de 10 environnements. Notre étude empirique montre que les besoins pour exprimer ce type de contraintes sont communs dans ces environnements et que notre approche est efficace pour les gérer

ETHOM: An Evolutionary Algorithm for Optimized Feature Models Generation (v. 1.2): Technical Report ISA-2012-TR-05

A feature model defines the valid combinations of features in a domain. The automated extraction of information from feature models is a thriving topic involving numerous analysis operations, techniques and tools. The progress of this discipline is leading to an increasing concern to test and compare the performance of analysis solutions using tough input models that show the behaviour of the tools in extreme situations (e.g. those producing longest execution times or highest memory consumption). Currently, these feature models are generated randomly ignoring the internal aspects of the tools under tests. As a result, these only provide a rough idea of the behaviour of the tools with average problems and are not sufficient to reveal their real strengths and weaknesses. In this technical report, we model the problem of finding computationally– hard feature models as an optimization problem and we solve it using a novel evolutionary algorithm. Given a tool and an analysis operation, our algorithm generates input models of a predefined size maximizing aspects as the execution time or the memory consumption of the tool when performing the operation over the model. This allows users and developers to know the behaviour of tools in pessimistic cases providing a better idea of their real power. Experiments using our evolutionary algorithm on a number of analysis operations and tools have successfully identified input models causing much longer executions times and higher memory consumption than random models of identical or even larger size. Our solution is generic and applicable to a variety of optimization problems on feature models, not only those involving analysis operations. In view of the positive results, we expect this work to be the seed for a new wave of research contributions exploiting the benefit of evolutionary programming in the field of feature modelling

A Formal Semantics for Feature Cardinalities in Feature Diagrams

Feature cardinalities in feature diagrams determine the num-ber of times a feature and its subtree can be duplicated dur-ing configuration by an operation named “cloning”. Other authors already investigated the problem and pub-lished different proposals of semantics for this construct. However, this previous work is not easily amenable to the formal study of the various properties of feature diagrams and their derived configurations. Also, cross-tree constraint languages still need to be properly extended to account for feature cardinalities. This paper presents an extension of an earlier formal se-mantics of feature diagrams by adding support for feature cardinalities. 1

ETHOM: An Evolutionary Algorithm for Optimized Feature Models Generation - TECHNICAL REPORT ISA-2012-TR-01 (v. 1.1)

A feature model defines the valid combinations of features in a domain. The automated extraction of information from feature models is a thriv ing topic involving numerous analysis operations, techniques and tools. The progress of this discipline is leading to an increasing concern to test and compare the performance of analysis solutions using tough input mod els that show the behaviour of the tools in extreme situations (e.g. those producing longest execution times or highest memory consumption). Cur rently, these feature models are generated randomly ignoring the internal aspects of the tools under tests. As a result, these only provide a rough idea of the behaviour of the tools with average problems and are not sufficient to reveal their real strengths and weaknesses. In this technical report, we model the problem of finding computationally– hard feature models as an optimization problem and we solve it using a novel evolutionary algorithm. Given a tool and an analysis operation, our algorithm generates input models of a predefined size maximizing aspects as the execution time or the memory consumption of the tool when per forming the operation over the model. This allows users and developers to know the behaviour of tools in pessimistic cases providing a better idea of their real power. Experiments using our evolutionary algorithm on a num ber of analysis operations and tools have successfully identified input mod els causing much longer executions times and higher memory consumption than random models of identical or even larger size. Our solution is generic and applicable to a variety of optimization problems on feature models, not only those involving analysis operations. In view of the positive results, we expect this work to be the seed for a new wave of research contributions exploiting the benefit of evolutionary programming in the field of feature modelling

Une approche basée sur les lignes de produits logiciels pour la configuration et adaptation des environments multi-nuages

Cloud computing is characterized by a model in which computing resources are delivered as services in a pay-as-you-go manner, which eliminates the need for upfront investments, reducing the time to market and opportunity costs. Despite its benefits, cloud computing brought new concerns about provider dependence and data confidentiality, which further led to a growing trend on consuming resources from multiple clouds. However, building multi-cloud systems is still very challenging and time consuming due to the heterogeneity across cloud providers' offerings and the high-variability in the configuration of cloud providers. This variability is expressed by the large number of available services and the many different ways in which they can be combined and configured. In order to ensure correct setup of a multi-cloud environment, developers must be aware of service offerings and configuration options from multiple cloud providers.To tackle this problem, this thesis proposes a software product line-based approach for managing the variability in cloud environments in order to automate the setup and adaptation of multi-cloud environments. The contributions of this thesis enable to automatically generate a configuration or reconfiguration plan for a multi-cloud environment from a description of its requirements. The conducted experiments aim to assess the impact of the approach on the automated analysis of feature models and the feasibility of the approach to automate the setup and adaptation of multi-cloud environments.Le cloud computing est caractérisé par un modèle dans lequel les ressources informatiques sont fournies en tant qu'un service d'utilité, ce qui élimine le besoin de grands investissements initiaux. Malgré ses avantages, le cloud computing a suscité de nouvelles inquiétudes concernant la dépendance des fournisseurs et la confidentialité des données, ce qui a conduit à l'émergence des approches multi-cloud. Cependant, la construction de systèmes multi-cloud est toujours difficile en raison de l'hétérogénéité entre les offres des fournisseurs de cloud et de la grande variabilité dans la configuration des fournisseurs de cloud. Cette variabilité est caractérisé par le grand nombre de services disponibles et les nombreuses façons différentes de les combiner et de les configurer. Afin de garantir la configuration correcte d'un environnement multi-cloud, les développeurs doivent connaître les offres de services et les options de configuration de plusieurs fournisseurs de cloud.Pour traiter ce problème, cette thèse propose une approche basée sur les lignes de produits logiciels pour gérer la variabilité dans les cloud afin d'automatiser la configuration et l'adaptation des environnements multi-cloud. Les contributions de cette thèse permettent de générer automatiquement un plan de configuration ou de reconfiguration pour un environnement multi-cloud à partir d'une description de ses exigences. Les expérimentations menées visent à évaluer l'impact de l'approche sur l'analyse automatisée des modèles de caractéristiques et la faisabilité de l'approche pour automatiser la configuration et l'adaptation des environnements multi-nuages