Flexible workflows to support transactional service composition in mobile environments

Service oriented computing provides suitable means to technically support distributed collaboration of heterogeneous devices, for example those present in mobile environments. E.g., many applications are built on composite Web- Services. However, when executing these applications in dynamic environments, failures of participating entities have to be optimistically coped with, in order to avoid inconsistent system states and thereby provide suitable correctness guarantees. Transactional coordination for services so far lacks the possibility to adapt failure handling to the current execution context, e.g. dynamically bound services at runtime. In this paper, we employ transactional service properties to ensure reliable, i.e., correct execution of workflows by still respecting the autonomy of participants. We propose algorithms to verifiy and alter the structure of the composition at runtime, thus adapting the control flow to the current execution context to ensure correct execution

Handling transactional business services.

This article discusses the handling of transactional business services, which are service compositions that orchestrate and coordinate underlying services to process a high-level business activity. The main contribution made in this article is the presentation of the pattern TBS handler, which describes how one can implement a transactional business service (TBS). This pattern functions as an overview pattern for a complete pattern language that is outlined in the text. This pattern language provides the appropriate ingredients for the implementation of a TBS. It is presented using thumbnails.

Web Services Support for Dynamic Business Process Outsourcing

Outsourcing of business processes is crucial for organizations to be effective, efficient and flexible. To meet fast-changing market conditions, dynamic outsourcing is required, in which business relationships are established and enacted on-the-fly in an adaptive, fine-grained way unrestricted by geographic distance. This requires automated means for both the establishment of outsourcing relationships and for the enactment of services performed in these relationships over electronic channels. Due to wide industry support and the underlying model of loose coupling of services, Web services increasingly become the mechanism of choice to connect organizations across organizational boundaries. This paper analyzes to which extent Web services support the dynamic process outsourcing paradigm. We discuss contract -based dynamic business process outsourcing to define requirements and then introduce the Web services framework. Based on this, we investigate the match between the two. We observe that the Web services framework requires further support for cross - organizational business processes and mechanisms for contracting, QoS management and process-based transaction support and suggest ways to fill those gaps

Towards an aspect weaving BPEL engine

This position paper proposes the use of dynamic aspects and the visitor design pattern to obtain a highly configurable and extensible BPEL engine. Using these two techniques, the core of this infrastructural software can be customised to meet new requirements and add features such as debugging, execution monitoring, or changing to another Web Service selection policy. Additionally, it can easily be extended to cope with customer-specific BPEL extensions. We propose the use of dynamic aspects not only on the engine itself but also on the workflow in order to tackle the problems of Web Service hot deployment and hot fixes to long running processes. In this way, composing aWeb Service "on-the-fly" means weaving its choreography interface into the workflow

Reliable scientific service compositions

Abstract. Distributed service oriented architectures (SOAs) are increas-ingly used by users, who are insufficiently skilled in the art of distributed system programming. A good example are computational scientists who build large-scale distributed systems using service-oriented Grid comput-ing infrastructures. Computational scientists use these infrastructure to build scientific applications, which are composed from basic Web ser-vices into larger orchestrations using workflow languages, such as the Business Process Execution Language. For these users reliability of the infrastructure is of significant importance and that has to be provided in the presence of hardware or operational failures. The primitives avail-able to achieve such reliability currently leave much to be desired by users who do not necessarily have a strong education in distributed sys-tem construction. We characterise scientific service compositions and the environment they operate in by introducing the notion of global scien-tific BPEL workflows. We outline the threats to the reliability of such workflows and discuss the limited support that available specifications and mechanisms provide to achieve reliability. Furthermore, we propose a line of research to address the identified issues by investigating auto-nomic mechanisms that assist computational scientists in building, exe-cuting and maintaining reliable workflows.

Verifying transactional requirements of web service compositions using temporal logic templates

Lecture notes in computer science, 2013, vol. 8180 LNCS (Part 1)Ensuring reliability in Web service compositions is of crucial interest as services are composed and executed in long-running, distributed mediums that cannot guarantee reliable communications. Towards this, transactional behavior has been proposed to handle and undo the effects of faults of individual components. Despite significant research interest, challenges remain in providing an easy-to-use, formal approach to verify transactional behavior of Web service compositions before costly development. In this paper, we propose the use of temporal logic templates to specify component-level and composition-level transactional requirements over a Web service composition. These templates are specified using a simple format, configured according to scope and cardinality, and automatically translated into temporal logic. To verify design conformance to a set of implemented templates, we employ model checking. We propose an algorithm to address state space explosion by reducing the models into semantically equivalent Kripke structures. Our approach facilitates the implementation of expressive transactional behavior onto existing complex services, as demonstrated in our experimental study.Scott Bourne, Claudia Szabo, and Quan Z. Shen

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

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

An Analysis of Service Ontologies

Services are increasingly shaping the world’s economic activity. Service provision and consumption have been profiting from advances in ICT, but the decentralization and heterogeneity of the involved service entities still pose engineering challenges. One of these challenges is to achieve semantic interoperability among these autonomous entities. Semantic web technology aims at addressing this challenge on a large scale, and has matured over the last years. This is evident from the various efforts reported in the literature in which service knowledge is represented in terms of ontologies developed either in individual research projects or in standardization bodies. This paper aims at analyzing the most relevant service ontologies available today for their suitability to cope with the service semantic interoperability challenge. We take the vision of the Internet of Services (IoS) as our motivation to identify the requirements for service ontologies. We adopt a formal approach to ontology design and evaluation in our analysis. We start by defining informal competency questions derived from a motivating scenario, and we identify relevant concepts and properties in service ontologies that match the formal ontological representation of these questions. We analyze the service ontologies with our concepts and questions, so that each ontology is positioned and evaluated according to its utility. The gaps we identify as the result of our analysis provide an indication of open challenges and future work