Monitoring safety properties of composite web services at runtime using CSP

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Modeling and Verification of Response Time of QoS-aware Web Service Composition by Timed CSP

The CSP (communicating sequential processes) method is useful for the development of sequence control mechanisms. From the specifications in CSP, one can investigate the nature and workings of a sequence control mechanism by the process composition calculation or algebra, prove deadlock absence by the algebra, and find the most suitable module structures of the control programs. In this paper, specifications of a silo system with concurrently working components are described in CSP, the movements are investigated by process composition calculations, and the deadlock absence of the system is proved by the calculations. Based on the discussions, specifications of a silo system with two source silos, two measuring hoppers, a mixer, two conveyors and two destination silos are described in CSP, and the system is implemented in the programming language Ada. The author's studies include the relation of CSP specifications to Ada programs. >

We propose an efficient method to detect conflicts, which may occur during the execution time of composite web services, based on model checking. The proposed method does not only check whether a composite service satisfies the correctness claims specified by a service developer, but it also detects any possible conflicts from the control and data flow of a composite service at the time of service development. The proposed method divides correctness claims into four types depending on their application time: pre/post-condition, policy, and assumption. Specifically, composite services and correctness claims are modelled by OWL-S and SWRL, respectively. The proposed method automatically converts the control and data flow of an OWLS composite service and the correctness claims into Promela code and LTL formulas, which are given as the input of a SPIN model checker. Experimental results under real-world scenarios show that the proposed method detects conflicts in composite web services effectively.

The Requirements to Design to Code (R2D2C) project of NASA's Software Engineering Laboratory is based on inferring a formal specification, currently using Communicating Sequential Processes (CSP), from system requirements supplied in the form of scenarios, a user-friendly medium often used to describe the behavior of computer systems under development. The scenarios are first converted into an intermediate form, CSP traces, from which are derived CSP specifications. This work, called Mise en Scene, defines a new medium (Scenario Notation Language, SNL) suitable for control-dominated systems, coupled with a two-stage process for automatic translation of scenarios to a new trace medium (Trace Notation Language, TNL) which encompasses CSP traces. A survey of the scenario concept and a small case study are also presented.

This paper introduces a cooperative service composition language called CCML which aims to facilitate the description of services, their interfaces and their behavior, further to reduce the complexity required to compose services. Interaction rules among services rely on a cooperative computation model, i.e. KPN (Kahn Process Network), which adopts dataflow and channel based asynchronous communication pattern among process nodes. Formal model for behavioral semantics of CCML is based on CCS process algebra which presents a high expressive power, capable of capturing CCML behavioral semantics. We give an operational semantics to CCML in the form of a labeled transition system (LTS) and describe the events of a LTS associated to the main CCML constructs, which are sequence, condition, loop and parallel. Finally, we present an application case to show how to describe service composition using CCML

In our previous paper [1], a new model of a Labeled Transition System (LTS)-type implementation was proposed. In ordinary LTSs, transitions are labeled by actions; therefore, they can be called LTSs of actions. The new model is an LTS of observations; in this model, observations and test actions (buttons) are used instead of actions. This model generalizes many testing semantics that are based on the LTS of actions but use additional observations (refusals, ready sets, etc.). Moreover, systems with priority, which are not described by the LTS of actions, are simulated uniformly. In the present paper, we develop this approach by focusing on the composition of systems. The point is that, on observation traces, one cannot define a composition with respect to which a composition of LTSs would possess the property of additivity: the set of traces of a composition of LTSs coincides with the set of all pairwise compositions of traces of LTS operands. This is explained by the fact that an observation in a composition state is not calculated based on observations in states-operands. In this paper, we propose an approach that eliminates this drawback. To this end, we label the transitions of LTSs by symbols (events) that, on the one hand, can be composed to guarantee the property of additivity, and, on the other hand, can be used to generate observations under testing: a transition by an event gives rise to an observation related to this event. This model is called an LTS of events. In this paper, we define (1) a transformation of an LTS of events into an LTS of observations to conform with the principles of our previous paper [1]; (2) a composition of LTSs of events; (3) a composition of specifications that preserves conformance: a composition of conformal implementations is conformal to a composition of specifications; and (4) a uniform simulation of LTSs of actions in terms of the LTSs of events, which allows one to consider an implementation in any interaction semantics admissible for LTSs of actions. In this case, a composition of LTSs of events obtained as a result of simulation of the original LTSs of actions is equivalent to the LTS of events obtained as a result of simulation of the composition of these LTSs of actions.

One of the major goals of Web services is to make easier their composition to form more complex services, modeled as workflows. A key role in the Web services composition is the selection of a proper service for each activity in the workflow. In general, this requires the exchange of sensitive information of users, requiring the composition, as well as of involved service providers. So far this problem has been investigated in the setting of orchestrated service composition, under the assumption of the presence of a broker coordinating the composition. However, a promising alternative approach is the one of choreography, where each service involved in the service composition has to locally manage service selection and invocation. In this paper, we propose a framework to enforce user and provider requirements in the scenario of service choreography in a privacy-preserving way, that is, without the releasing of any private information of users and providers. To achieve this result we make use of different privacy-preserving protocols. As it will be shown in the paper, the proposed solution does not implies relevant overhead.

Managing Service Level Agreement (SLA) for composite semantic web services is a very complex process, as it involves many complex tasks such as components discovery, provisioning, monitoring, recovery, and coordination. Indeed, managing all these tasks manually is a very cumbersome operation, nevertheless it is time consuming and prone to errors. To overcome such problems, automated SLA management for composite semantic web services is needed. This requires the SLA of the composite service to be described in a machine-understandable format such that it can be understood and processed by the automated SLA management tool. Currently, there is no SLA description language for composite semantic web services, but there exists an SLA description language for atomic web services, known as the Web Service Level Agreement (WSLA). Hence, in this paper, we aim to extend the WSLA language to describe composite semantic web services' SLAs, then we show how we can automatically generate the components' SLAs from the composite semantic web services' SLAs; adopting the CRECENT framework that we previously proposed for managing composite web services.

The behavior of embedded hardware and software systems is determined by at least three dimensions: control flow, data aspects, and real-time requirements. To specify the different dimensions of a system with the best-suited techniques, the formal language CSP-OZ-DC (Hoenicke and Maier, 2005) integrates communicating sequential processes (CSP) (Hoare, 1985), Object-Z (OZ) (Smith, 2000), and duration calculus (DC) (Zhou and Hansen, 2004) into a declarative formalism equipped with a unified and compositional semantics. In this paper, we provide evidence that CSP-OZ-DC is a convenient language for modeling systems of industrial relevance. To this end, we examine the emergency message handling in the European train control system (ETCS) as a case study with uninterpreted constants and infinite data domains. We automatically verify that our model ensures real-time safety properties, which crucially depend on the system's data handling. Related work on ETCS case studies focuses on stochastic examinations of the communication reliability (Hermanns et al., 2005; Zimmermann and Hommel, 2005). The components' data aspects are neglected, though

The Business Process Execution Language (BPEL) has become the standard in Web service composition, so that been adopted by industries to create mission critical services. The business process reliability especially business process consistency when some services failed is critical to composite services especially involving various organizations. However, it is difficult to conduct business process reliability testing for composite services due to complex business process in service composition, remote deployed services and long time testing duration. Little research is done to test fault tolerance capabilities of composite services only from low level. This paper proposes a technique on how to test the reliability of composite service defined in BPEL from the view of business semantics with little cost using fault injection. We present an approach for reliability testing of web services by using service stubs with semantic faults instead of real services which can be placed at service provider side or service consumer side. Dislike existing studies, we focus on how to find the reliability problems associating with business process - called semantics as the problems are not pure coding error but faults related to business process. In addition, the behavior of composite services in BPEL is analyzed when there are faults in orchestrated services invoked. Finally, a case study is given to show the whole process of reliability testing for composite web service.

The Web service composition problem involves the creation of a choreographer that provides the interaction between a set of component services to realize a goal service. Several methods have been proposed and developed to address this problem. In this paper, we consider those scenarios where the composition process may fail due to incomplete specification of goal service requirements or due to the fact that the user is unaware of the functionality provided by the existing component services. In such cases, it is desirable to have a composition algorithm that can provide feedback to the user regarding the cause of failure in the composition process. Such feedback will help guide the user to re-formulate the goal service and iterate the composition process. We propose a failure analysis technique for composition algorithms that views Web service behavior as multiple sequences of input/output events. Our technique identifies the possible cause of composition failure and suggests possible recovery options to the user. We discuss our technique using a simple e-Library Web service in the context of the MoSCoE Web service composition framework.KeywordsFailure AnalysisService CompositionComposite ServiceLabel Transition SystemComposition ProcessThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

In software markets of the future, customer-specific software will be developed on demand based on distributed software and hardware services. Based on a customer-specific request, available service offers have to be discovered and composed into sophisticated IT services that fulfill the customer's request. A prerequisite of this vision are rich service descriptions, which comprise structural as well as behavioral aspects of the services, otherwise an accurate service discovery and composition is not possible. However, automatic matching of service requests and offers specified in rich service descriptions for the purpose of service discovery is a complex task, due to the multifaceted heterogeneity of the service partners. This heterogeneity includes the use of different specification languages, different underlying ontologies, or different levels of granularity in the specification itself. In this article, we present a comprehensive approach for service discovery and composition, which overcomes the underlying heterogeneity of the service partners. Based on a realistic case study of our industrial partner from the e-tourism domain, we first introduce an automatic matching mechanism for service requests and offers specified in a rich service description language. In addition, we propose an automatic service composition approach, which determines possible service compositions by composing the service protocols through a composition strategy based on labeled transition systems.

How to manage composite service rather than single service becomes a new challenge in SOA and cloud based enterprise IT environment. This paper proposes a novel scheme, E-WS-Man, extending the WS-Management standard to support management of composite services. First, we design E-WS-Man management model and system architecture. After that we discuss E-WS-Man prototype system design and implementation scheme, including Web Service resources construction, Management Middleware Layer design, and Multi-agents assisted management scheme design. After that we describe the prototype system testing experiment. With the support of multiagent technology, experimental results verify that our scheme can extend the WS-Management specification to efficiently manage heterogeneous composite Web services with a unified management interfaces. Finally, we conclude this paper and present future research direction.

Service composition combines a set of available Web services using control flows to create a more complex service. The service composition is a complex process which is challenging even for experienced users to discover and select appropriate service among a set of similar services. The available tools and techniques for service composition either are too complicated or require technical knowledge (such as script language). Moreover the heterogeneity in service description language and communication protocols make service composition more difficult. In our research, we propose an approach that allows non-technical users (i.e., end users) to easily compose heterogeneous Web resources with different communication protocol. The goal of this research is fulfilled on two stages: 1) identifying integrable Web resources from different Web applications and SOAP-based Web services; and 2) providing approaches to discover and compose Web resources that are capable of accomplishing user's activities. We propose a framework that assists a user to discover and compose services.