Issues about the Adoption of Formal Methods for Dependable Composition of Web Services

Web Services provide interoperable mechanisms for describing, locating and invoking services over the Internet; composition further enables to build complex services out of simpler ones for complex B2B applications. While current studies on these topics are mostly focused - from the technical viewpoint - on standards and protocols, this paper investigates the adoption of formal methods, especially for composition. We logically classify and analyze three different (but interconnected) kinds of important issues towards this goal, namely foundations, verification and extensions. The aim of this work is to individuate the proper questions on the adoption of formal methods for dependable composition of Web Services, not necessarily to find the optimal answers. Nevertheless, we still try to propose some tentative answers based on our proposal for a composition calculus, which we hope can animate a proper discussion

Distribution pattern-driven development of service architectures

Distributed systems are being constructed by composing a number of discrete components. This practice is particularly prevalent within the Web service domain in the form of service process orchestration and choreography. Often, enterprise systems are built from many existing discrete applications such as legacy applications exposed using Web service interfaces. There are a number of architectural configurations or distribution patterns, which express how a composed system is to be deployed in a distributed environment. However, the amount of code required to realise these distribution patterns is considerable. In this paper, we propose a distribution pattern-driven approach to service composition and architecting. We develop, based on a catalog of patterns, a UML-compliant framework, which takes existing Web service interfaces as its input and generates executable Web service compositions based on a distribution pattern chosen by the software architect

Semantic model-driven development of service-centric software architectures

Service-oriented architecture (SOA) is a recent architectural paradigm that has received much attention. The prevalent focus on platforms such as Web services, however, needs to be complemented by appropriate software engineering methods. We propose the model-driven development of service-centric software systems. We present in particular an investigation into the role of enriched semantic modelling for a modeldriven development framework for service-centric software systems. Ontologies as the foundations of semantic modelling and its enhancement through architectural pattern modelling are at the core of the proposed approach. We introduce foundations and discuss the benefits and also the challenges in this context

WSCDL to WSBPEL: A Case Study of ATL-based Transformation

The ATLAS Transformation Language (ATL) is a hybrid transformation language that combines declarative and imperative programming elements and provides means to define model transformations. Most transformations using ATL reported in the literature show a simplified use of ATL, and often involve a single transformation. However, in more realistic situations, multiple transformations may be necessary, especially in case the original input/output models are not represented in the metametamodeling representation expected by the transformation engine. In this paper, we discuss a model transformation from service choreography (WSCDL) to service orchestration (WSBPEL), which cannot be performed in a single ATL transformation due to the mismatch between the concrete XML syntax of these languages and the metametamodeling representation expected by the ATL transformation engine. This requires auxiliary transformations in which this mismatch is resolved. In principle, the required auxiliary transformations can be implemented using XSLT or a general-purpose programming language like Java. However, in our case study, we evaluate the use of ATL to perform these transformations. We exploit ATL by leveraging the ATL's XML\ud injection and the XML extraction mechanisms to perform the overall transformation in terms of a transformation chain

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

Context constraint integration and validation in dynamic web service compositions

System architectures that cross organisational boundaries are usually implemented based on Web service technologies due to their inherent interoperability benets. With increasing exibility requirements, such as on-demand service provision, a dynamic approach to service architecture focussing on composition at runtime is needed. The possibility of technical faults, but also violations of functional and semantic constraints require a comprehensive notion of context that captures composition-relevant aspects. Context-aware techniques are consequently required to support constraint validation for dynamic service composition. We present techniques to respond to problems occurring during the execution of dynamically composed Web services implemented in WS-BPEL. A notion of context { covering physical and contractual faults and violations { is used to safeguard composed service executions dynamically. Our aim is to present an architectural framework from an application-oriented perspective, addressing practical considerations of a technical framework