Adaptation of Asynchronously Communicating Software

International audienceSoftware adaptation techniques aim at generating new components called adapters, which make a set of services work correctly together by compensating for existing mismatch. Most approaches assume that services interact synchronously using rendez-vous communication. In this paper, we focus on asynchronous communication, where services interact exchanging messages via buffers. We overview a method for automatically generating adapters in such asynchronous environments

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

Adaptation of Asynchronously Communicating Software

International audienceSoftware adaptation techniques aim at generating new components called adapters, which make a set of services work correctly together by compensating for existing mismatch. Most approaches assume that services interact synchronously using rendez-vous communication. In this paper, we focus on asynchronous communication, where services interact exchanging messages via buffers. We overview a method for automatically generating adapters in such asynchronous environments

Expressive Equivalence and Succinctness of Parametrized Automata with respect to Finite Memory Automata

International audienceWe compare parametrized automata, a class of automata recently introduced by the authors, against finite memory automata with non-deterministic assignment, an existing class of automata used to model services. We prove that both classes have the same expressive power, while parametrized automata can be exponentially succinct in some cases. We then prove that deciding simulation preorder for parametrized automata is EXPTIME-complete, extending an earlier result showing it in EXPTIME

Distilling structure in Taverna scientific workflows: a refactoring approach

BACKGROUND: Scientific workflows management systems are increasingly used to specify and manage bioinformatics experiments. Their programming model appeals to bioinformaticians, who can use them to easily specify complex data processing pipelines. Such a model is underpinned by a graph structure, where nodes represent bioinformatics tasks and links represent the dataflow. The complexity of such graph structures is increasing over time, with possible impacts on scientific workflows reuse. In this work, we propose effective methods for workflow design, with a focus on the Taverna model. We argue that one of the contributing factors for the difficulties in reuse is the presence of "anti-patterns", a term broadly used in program design, to indicate the use of idiomatic forms that lead to over-complicated design. The main contribution of this work is a method for automatically detecting such anti-patterns, and replacing them with different patterns which result in a reduction in the workflow's overall structural complexity. Rewriting workflows in this way will be beneficial both in terms of user experience (easier design and maintenance), and in terms of operational efficiency (easier to manage, and sometimes to exploit the latent parallelism amongst the tasks). RESULTS: We have conducted a thorough study of the workflows structures available in Taverna, with the aim of finding out workflow fragments whose structure could be made simpler without altering the workflow semantics. We provide four contributions. Firstly, we identify a set of anti-patterns that contribute to the structural workflow complexity. Secondly, we design a series of refactoring transformations to replace each anti-pattern by a new semantically-equivalent pattern with less redundancy and simplified structure. Thirdly, we introduce a distilling algorithm that takes in a workflow and produces a distilled semantically-equivalent workflow. Lastly, we provide an implementation of our refactoring approach that we evaluate on both the public Taverna workflows and on a private collection of workflows from the BioVel project. CONCLUSION: We have designed and implemented an approach to improving workflow structure by way of rewriting preserving workflow semantics. Future work includes considering our refactoring approach during the phase of workflow design and proposing guidelines for designing distilled workflows

Quality of Service Conflict During Web Service Monitoring: A Case Study

AbstractWeb services have become one of the most used technologies in service-oriented systems. Its popularity is due to its property to adapt to any context. As a consequence of the increasing number of Web services on the Internet and its important role in many applications today, Web service quality has become a crucial requirement and demanded by service consumers. Terms of quality levels are written between service providers and service consumers to ensure a degree of quality. The use of monitoring tools to control service quality levels is very important. Quality attributes suffer variations in their values during runtime, this is produced by many factors such as a memory leak, deadlock, race data, inconsistent data, etc. However, sometimes monitoring tools can impact negatively affecting the quality of service when they are not properly used and configured, producing possible conflicts between quality attributes. This paper aims to show the impact of monitoring tools over service quality, two of the most important quality attributes – performance and accuracy – were chosen to be monitored. A case study is conducted to present and evaluate the relationship between performance and accuracy over a Web service. As a result, conflict is found between performance and accuracy, where performance was the most affected, because it presented a degradation in its quality level during monitoring

A pattern-based approach for designing reliable cyber-physical systems

Cyber-Physical Systems (CPS) appear to be of paramount importance due to their increasing use on critical infrastructure. New challenges have occurred because of the nature and the complexity of such systems in supporting heterogeneous physical and cyber components simultaneously. Failures or attacks on system components decrease system reliability creating severe consequences to CPS and the attached applications. The construction of complex CPS with respect to security and dependability (SandD) properties is necessary to avoid system vulnerabilities at design level. Design patterns are solutions for reusable designs and interactions of objects. In this work we present a pattern-based language for designing CPS able to guarantee SandD properties. The first set of SandD patterns includes the Reliability Component Composition (RCC) Patterns for designing reliable CPS. RCC patterns are encoded in Drools, which is a rule-based reasoning system. To evaluate our approach, we use RCC patterns as a methodology for designing a reliable wireless sensor network attached to a physical architecture to send monitored data to a central controller through relay nodes and paths

Dynamic adaptation of service compositions with variability models

Web services run in complex contexts where arising events may compromise the quality of the whole system. Thus, it is desirable to count on autonomic mechanisms to guide the self-adaptation of service compositions according to changes in the computing infrastructure. One way to achieve this goal is by implementing variability constructs at the language level. However, this approach may become tedious, difficult to manage, and error-prone. In this paper, we propose a solution based on a semantically rich variability model to support the dynamic adaptation of service compositions. When a problematic event arises in the context, this model is leveraged for decision-making. The activation and deactivation of features in the variability model result in changes in a composition model that abstracts the underlying service composition. These changes are reflected into the service composition by adding or removing fragments of Business Process Execution Language (WS-BPEL) code, which can be deployed at runtime. In order to reach optimum adaptations, the variability model and its possible configurations are verified at design time using Constraint Programming. An evaluation demonstrates several benefits of our approach, both at design time and at runtime.This work has been developed with the support of MICINN under the project everyWare TIN2010-18011 and co-financed with ERDF.Alférez Salinas, GH.; Pelechano Ferragud, V.; Mazo, R.; Salinesi, C.; Díaz, D. (2014). Dynamic adaptation of service compositions with variability models. Journal of Systems and Software. 91:24-47. https://doi.org/10.1016/j.jss.2013.06.034S24479