Integrating heterogeneous web services from an end user perspective

The vision of the Semantic Web is to reduce manual discovery and usage of Web resources (documents and services) and to allow software agents to automatically identify these Web resources, integrate them and execute them for achieving the intended goals of the user. Such a composed Web service may be represented as a workflow, called service flow. Current studies of Web services are not sufficient for automatic composition. This paper presents different types of compositional knowledge required for Web service discovery and composition: syntactic, semantic and pragmatic knowledge. As a proof of concept, we have implemented our framework in a cardiovascular domain which requires advanced service discovery and composition across heterogeneous platforms of multiple organizations. Within this framework, we describe (1) How to represent the compositional knowledge, which plays a role in service discovery and composition, in DAML-S; (2) How heterogeneous medical services intemperate in a composed medical service flow. (3) To solve this knowledge level integration, we build on an ontology integration method called SEMIO (Semantic Interoperability).

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.

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.

New value-added business, generated by Web service composition in BPEL, provides more powerful and flexible features. SOAP-based web services invoked in BPEL are heavy with redundant information and lower performance. RESTful Web service is brought forward to new value-added business as an alternative solution. However, it's a big challenge to compose RESTful Web services with SOAP-based Web Services in SOA BPEL business processes. BPEL is not designed to use RESTful Web services because these types of services do not use WSDL to describe themselves. This paper proposes a novel approach for integrating RESTful Web services and SOAP-based Web services in business processes described in BPEL. The approach is applied to a practical multimedia conference BPEL process, and the experimental data show the stability of the new RESTful BPEL process with a higher performance.

Combining quantitative constraints with qualitative preferences for effective non-functional properties-aware service composition

A web service is a software system that supports interoperable machine to machine interaction over the network. It can be any kind of service provided on the web that can exchange data between applications. In simple terms, it is any program that is callable by another program across the web using standard protocols. Web services are special because they are independent of the platform, programming language, and model design. In current web applications, more businesses are gradually publishing their business as services over the web. This growing number of web services available within an organization and on the Web raises a new and challenging search problem: locating desired web services. Searching for web services with conventional web search engines is insufficient in this context. In this paper, a latent semantic web service discovery and composition framework, addressing both discovery and composition of web services, is introduced. The framework provides a graphical visualization interface that can facilitate users in finding the desired web service beyond the general keyword search and provide composition of complex services if the service does not exist. A novel approach based on an information retrieval technique known as latent semantic analysis is applied to a large web service descriptions data set collection. By using co-occurrence patterns across the entire data collection, and then using those patterns to infer semantic relationships between documents, relevant results in a ranked order can be retrieved. Moreover, a back to front algorithm is applied to the composition search interface in order to compose complex web services in full or partial terms from pre-existing web services when the requested service does not exist. An experimental study conducted on a collection of 2525 publicity available web service shows improved performance to the technique applied in obtaining much better search results.

Although web service technology is becoming more prevalent the mechanisms for advertising and discovering web services are still at a rudimentary stage. WSDL provides information about service name and parameters for the purpose of invocation. UDDI provides a set of WSDL documents matching keywords in a query. The aim of the Mathematics On the NET (MONET) project is to deliver a proof-of-concept demonstration of a framework for mathematical web services which uses semantic web technologies to broker between user requirements and deployed services. This requires mechanisms for describing mathematical objects and properties so that a piece of software can evaluate the applicability of a particular service to a given problem. Thus we describe our Mathematical Service Description Language (MSDL), with its ontological grounding in OpenMath and outline its role in service brokerage and service composition within MONET. We believe similar issues arise in many other (scientific) domains, and the leverage obtained here, through the formal background of mathematics, suggests a road-map for the development of similar domain-specific service description languages.

Service Oriented Architecture (SOA) has been widely adopted by industries due to its ability to provide increased interoperability among heterogeneous systems. SOA is realized through web services which can be either based on the style of Remote Procedure call(RPC) and SOAP protocol or on the Representational State Transfer(REST) style and HTTP. RESTful web services are increasingly becoming popular in the industry because of their simplicity, uniform interface, statelessness and cacheability benefits. The ability to efficiently select and integrate appropriate heterogeneous services available on the web dynamically at runtime is essential in the development of the applications based on web services. Whenever a single web service cannot satisfy the functionality required by the user, there should be a possibility to combine several existing services together in order to fulfill the request. This need has triggered a considerable number of research efforts on the composition of web services. Although several works have focused on the composition of SOAP based web services, there has not been adequate effort towards the composition of RESTful services. However, due to the above- mentioned advantages offered by the RESTful web services, it will be beneficial to design an application as a composition of such RESTful services. Towards this objective, this paper investigates two different approaches for composing the REStful web services specifically designed for health care domain, one using the Jopera tool and another using hypermedia.

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.

Web services technologies change the software industry drastically by developing and integrating enterprise web services and applications in order to enable the users to access them. There are several research initiatives in the field of Web services for enterprise applications. However, none of the initiatives have attempted for web applications pertaining to academic institution using Web services technology. Web service composition is the combination of web services from different service providers to create a more sophisticated, value added web service to the web users. Researchers put on efforts to bring out the state-of-the art in web services technologies and security technologies for web services. The composition of web services is another promising area for research and development. A study reveals that there are number of approaches providing secure web services. However, there is no attempt made so far to secure the services at multi-level. This paper proposes a Multi-level Secured Framework (MLSF) for the students, faculty and employees of the academic institutions which provides secured composite web services such as admission service, fees payment service, library service, personalized service and so on. The MLSF enhances the security at various levels such as user level, device level, web services level and institution level.

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.

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 article describes a method for developing and modelling composite web-services. Web-service composition is used to derive new functionality from the interaction of existing web-services. Composite web-services are built in several stages: specifications (determining the type of service); development of the structure of the service based on the algebra of services; service composition modelling; selecting a service variant and generating a service. The main elements of the proposed approach are the algebra of services and web-services interaction models (basic and composite). The above approach formally presents the consideration of the main aspects in solving problems related to the construction of effective composite web-services and the selection of mathematical models, namely: description of web-services, determining the structure of web-services, taking into account the dynamics of information changes, taking into account the main uncertainties in building the structure web-services. Based on the approach, a method for constructing composite web-services has been developed. The method is based on an algebraic description of a web-service based on a specialized algebra of services. The method consists of the following steps: description of the task of developing a web-service; development of the structure of a web service based on the algebra of services; formal description of the structure and clarification of service operations; building models of functioning and interaction of service components; building simulation models of the composite service; defining the final structure of the composite service; web-service implementation. The main tool for describing composite services is the algebra of services, and the model building tool is colouredPetri nets implemented using СPN Tools. As an example of the application of the developed method, the construction of a pharmaceutical service is described, in which the modellingof the interaction of web-services based on Petri nets is used. The process of building a composite model of a web-service is considered. The process begins with building a pharmaceutical web-service model structure based on the service algebra. Based on the service algebra, operators were developed to implement composite services. The structure of the model is developed, which is presented in the form of a formal description. The process of building pharmaceutical service models in the СPN Tools environment is described in detail.

Semantic Web services have become a core technology in developing business operation on the Web. Web service composition is an important activity to leverage the use of semantic Web services. Several composition systems have been proposed to meet this need. However, these systems only support a particular Web service description language such as OWL-S or WSMO, thus limiting the capability of invoking the services available from various sources over the Internet. This paper introduces a Web service composition system which supports multiple service description languages. As of practical aspect, we have implemented the system supporting the two most popular service description languages, i.e. OWL-S and WSMO. However, our design is left open to support additional language if. needed. The composition algorithm employed in our system is based on an existing composition algorithm for OWL-S Web service but it is extended to support WSMO. An example will be introduced to present how the system works.

Web services – a new breed of self-contained, self-describing, modular applications published, located, and invoked across the Web – handle functions, from simple requests to complicated business processes. They are defined as network-based application components with a services-oriented architecture (SOA) using standard interface description languages and uniform communication protocols. SOA enables organizations to grasp and respond to changing trends and to adapt their business processes rapidly without major changes to the IT infrastructure. The Inaugural International Conference on Next-Generation Web Services Practices (NWeSP'05) attracted researchers who are also the world's most respected authorities on the semantic Web, Web-based services, and Web applications and services. NWeSP'05 was held in cooperation with the IEEE Computer Society Task Force on Electronic Commerce, the Technical Committee on Internet, and the Technical Committee on Scalable Computing. This special issue presents eight papers focused on different aspects of Web services and their applications. Papers were selected based on fundamental ideas and concepts rather than the thoroughness of techniques employed. Papers are organized as follows: <I>Taher et al.</I> present the first paper, on a Quality of Service Information and Computational framework (QoS-IC) supporting QoS-based service selection for SOA. The framework's functionality is expanded using a QoS constraints model that establishes an association relationship between different QoS properties and is used to govern QoS-based service selection in the underlying algorithm. Using a prototype implementation, the authors demonstrate how QoS constraints improve QoS-based service selection and save consumers valuable time. Due to the complex infrastructure of web applications, response times perceived by clients may be significantly longer than desired. To overcome some of the current problems, <I>Vilas et al.</I>, in the second paper, propose a cache-based extension of the architecture that enhances the current web services architecture, which is mainly based on program-logic or protocol-dependent optimization. In the third paper, Jo and Yoo present authorization for securing XML sources on the Web. One of the disadvantages of existing access control is that the DOM tree must be loaded into memory while all XML documents are parsed to generate the DOM tree, such that a lot of memory is used in repetitive search for tree to authorize access to all nodes in the DOM tree. The complex authorization evaluation process required thus lowers system performance. Existing access control fails to consider information structure and semantics sufficiently due to basic HTML limitations. The authors overcome some of these limitations in the proposed model. In the fourth paper, Jung and Cho propose a novel behavior-network-based method for Web service composition. The behavior network selects services automatically through internal and external links with environmental information from sensors and goals. An optimal service is selected at each step, resulting in a globally optimal service sequence for achieving preset goals. The authors detail experimental results for the proposed model by comparing them with rule-based system and user tests. <I>Kong et al.</I> present an efficient method in the fifth paper for merging heterogeneous ontologies – no ontology building standard currently exists – and the many ontology-building tools available are based on different ontology languages, mostly focusing on how to create, edit and infer the ontology efficiently. Even ontologies about the same domain differ because ontology experts hold different view points. For these reasons, interoperability between ontologies is very low. The authors propose merging heterogeneous domain ontologies by overcoming some of the above limitations. In the sixth paper, Chen and Che provide polynomial-time tree pattern query minimization algorithm whose efficiency stems from two key observations: (i) Inherent redundant "components" usually exist inside the rudimentary query provided by the user, and (ii) nonedundant nodes may become redundant when constraints such as co-occurrence and required child/descendant are given. They show that the algorithm obtained by first augmenting the input tree pattern using constraints, then applying minimization, invariably finds a unique minimal equivalent to the original query. Chen and Che present a polynomial-time algorithm for tree pattern query (TPQ) minimization without XML constraints in the seventh paper. The two-part algorithm is a dynamic programming strategy for finding all matching subtrees within a TPQ. The algorithm consists of one for subtree recognization and a second for subtree deletion. In the last paper, <I>Bagchi et al.</I> present the mobile distributed virtual memory (MDVM) concept and architecture for cellular networks containing server-groups (SG). They detail a two-round randomized distributed algorithm to elect a unique leader and co-leader of the SG that is free of any assumption about network topology, and buffer space limitations and is based on dynamically elected coordinators eliminating single points of failure. As guest editors, we thank all authors featured in this special issue for their contributions and the referees for critically evaluating the papers within the short time allotted. We sincerely believe that readers will share our enjoyment of this special issue and find the information it presents both timely and useful.