Semantic web service composition in IRS-III: The structured approach

Semantic Web Services facilitate activities including automatic discovery and composition of Web Services. Research initiatives such as WSMO have been developing specifications for this technology. This paper describes a model for composition of Web services. The proposed model complements the WSMO orchestration in IRS-III, a framework for Semantic Web Services based on WSMO specification. We present a tool based on the above model that supports a user-guided interactive composition approach, by recommending component Web services according to the composition context

MAPPING BPEL PROCESSES TO DIAGNOSTIC MODELS

Web services are loosely-coupled, self-contained, and self-describing software modules that perform a predetermined task. These services can be linked together to develop an appli­ cation that spans multiple organizations. This linking is referred to as a composition of web services. These compositions potentially can help businesses respond more quickly and more cost-effectively to changing market conditions. Compositions can be specified using a high- level workflow process language. A fault or problem is a defect in a software or software component. A system is said to have a failure if the service it delivers to the user deviates from compliance with the system specification for a specified period of time. A problem causes a failure. Failures are often referred to as symptoms of a problem. A problem can occur on one component but a failure is detected on another component. This suggests a need to be able to determine a problem based on failures. This is referred to as fault diagnosis. This thesis focuses on the design, implementation and evaluation of a diagnostic module that performs automated mapping of a high-level specification of a web services composition to a diagnostics model. A diagnosis model expresses the relationship between problems and potential symptoms. This mapping can be done by a third party service that is not part of the application resulting from the composition of the web services. Automation will allow a third party to do diagnosis for a large number of compositions and should be less error-prone

A component-based approach to automated web service composition

There is great promise in the idea of having Web services available on the Internet, that can be flexibly composed to achieve more complex services, which can themselves then also be used as components in other contexts. However it is challenging to realise this idea, without essentially programming the composition using some process language such as WS-BPEL or OWL-S process descriptions. This paper presents a mechanism for specifying the external interface to composite and component services, and then deriving an appropriate internal model to realise a functioning composition. We present a conversation specification language for defining interaction protocols and investigate the issue of synchronous and asynchronous communication between the composite service and the component service

Model-Based Testing for Composite Web Services in Cloud Brokerage Scenarios

Cloud brokerage is an enabling technology allowing various services to be merged together for providing optimum quality of service for the end-users. Within this collection of composed services, testing is a challenging task which brokers have to take on to ensure quality of service. Most Software-as-a-Service (SaaS) testing has focused on high-level test generation from the functional specification of individual services, with little research into how to achieve sufficient test coverage of composite services. This paper explores the use of model-based testing to achieve testing of composite services, when two individual web services are tested and combined. Two example web services – a login service and a simple shopping service – are combined to give a more realistic shopping cart service. This paper focuses on the test coverage required for testing the component services individually and their composition. The paper highlights the problems of service composition testing, requiring a reworking of the combined specification and regeneration of the tests, rather than a simple composition of the test suites; and concludes by arguing that more work needs to be done in this area

Fault Tolerance Framework for Composite Web Services

A composite Web service combines multiple, logically interrelated services for creating more common services meeting complex requirements from users. The services participating in a composition coordinate the actions of distributed activity using Web services protocols to reach consistent agreement on the outcome of joint operation. However, as services run over unreliable protocols, there is a great chance that services fail due to the failure of protocols. However, current protocol standards provide fault-tolerance but are limited to backward recovery using expensive compensation and roll-back strategies. This paper gives an extension of the existing Web services business activity (WS-BA) protocol to deal with failures using forward recovery approach. A set of common failure types affecting the execution of component services is identified, and recovery solutions for each identified failure are also presented. The fault-handling extension of the WS-BA protocol implements recovery solutions for each of the identified failures to handle failures at runtime. Another important aspect about which the WS-BA protocol specification is unclear is reaching and notifying consistent outcome on the completion of joint work. This study extends the WS-BA protocol to notify consistent outcome reached by all participating services. The implementation and testing of the framework are performed using the model-checking and verification tool UPPAAL. A well-known application example supports the study. The key properties of the framework, like the execution of corresponding recovery actions in cases of failures and reaching a consistent agreement on the outcome of joint operation, are verified

Aspect-Oriented Techniques for Web Services: a Model-Driven Approach

Web Service technologies offer a successful way for interoperability among applications, but in order to tackle the entire web service life cycle, it is necessary to face how to model systems based on service functionality and also how to add extra-functional properties to modelled services. In this regard, we propose first of all a versatile and simple UML profile based on the Service Component Architecture specification for modelling services, in order to provide a model environment in which to add extra-functional properties. Secondly, a new UML profile is proposed to model and reuse the said extra-functional properties in service models. The implemented models based on these profiles will be independent from a final implementation language or platform, thus it is necessary to specify a particular type of model to convert the independent one into in a subsequent step. In order to meet this requirement an object, an aspect and a policy based models are proposed as the intermediate step between the independent model and the final code. We acknowledge that there are tools available which convert Java models into web services\u27 Java code, and it is not our aim to build a tool to fulfil this requirement. Regarding extra-functional properties, aspect-oriented techniques allow them to be easily modularized and reused; in this respect, properties are implemented as aspects in a totally transparent way and avoid the need to modify service code in an intrusive manner on adding extra-functional properties, improving our system maintenance. Furthermore, this way traceability between the model and the code is perfectly maintained in both directions. This work has been developed thanks to the support of CICYT under contract TIN2005-09405-C02-02

Specifying and verifying communities of Web services using argumentative agents

This thesis includes two main contributions: the first one is specifying the use of argumentative agents in the design and development of communities of Web services; the second is using a formal technique to verify communication protocols against given properties for these communities. Web services that provide a similar functionality are gathered into a single community, independently of their origins, locations, and ways of doing. Associating Web services with argumentative agents that are able to persuade and negotiate with others organizes these Web services in a better way so that they can achieve the goals they set in an efficient way. A community is led by a master component, which is responsible among others for attracting new Web services to the community, retaining existing Web services in the community, and identifying the Web services in the community that will participate in composite scenarios. Besides FIPA-ACL, argumentative dialogue games are also used for agent interaction. In this thesis, we use tableau-based model checking algorithm to verify our argumentative agent-base community of Web services negotiation protocol. This algorithm aims at verifying systems designed as a set of autonomous interacting agents. We provide the soundness, completeness, termination and complexity results. We also simulate our specification with Jadex BDI programming language and implement our verification with a modified and enhanced version of CWB-NC model checker. Keywords. Multi-agent systems, BDI agent architecture, model checking, agent oriented programming, FIPA-ACL, dialogue game, agent-based negotiation protocol, Jadex, CWB-NC

Integrating web services into data intensive web sites

Designing web sites is a complex task. Ad-hoc rapid prototyping easily leads to unsatisfactory results, e.g. poor maintainability and extensibility. However, existing web design frameworks focus exclusively on data presentation: the development of specific functionalities is still achieved through low-level programming. In this paper we address this issue by describing our work on the integration of (semantic) web services into a web design framework, OntoWeaver. The resulting architecture, OntoWeaver-S, supports rapid prototyping of service centred data-intensive web sites, which allow access to remote web services. In particular, OntoWeaver-S is integrated with a comprehensive web service platform, IRS-II, for the specification, discovery, and execution of web services. Moreover, it employs a set of comprehensive site ontologies to model and represent all aspects of service-centred data-intensive web sites, and thus is able to offer high level support for the design and development process

Model Based Development of Quality-Aware Software Services

Modelling languages and development frameworks give support for functional and structural description of software architectures. But quality-aware applications require languages which allow expressing QoS as a first-class concept during architecture design and service composition, and to extend existing tools and infrastructures adding support for modelling, evaluating, managing and monitoring QoS aspects. In addition to its functional behaviour and internal structure, the developer of each service must consider the fulfilment of its quality requirements. If the service is flexible, the output quality depends both on input quality and available resources (e.g., amounts of CPU execution time and memory). From the software engineering point of view, modelling of quality-aware requirements and architectures require modelling support for the description of quality concepts, support for the analysis of quality properties (e.g. model checking and consistencies of quality constraints, assembly of quality), tool support for the transition from quality requirements to quality-aware architectures, and from quality-aware architecture to service run-time infrastructures. Quality management in run-time service infrastructures must give support for handling quality concepts dynamically. QoS-aware modeling frameworks and QoS-aware runtime management infrastructures require a common evolution to get their integration