Knowledge Extraction from Web Services Repositories

chapter 3 - Web Services

Web service is a technological solution for software interoperability that supports the seamless integration of diverse applications. In the vision of web service architecture, web services are described by the Web Service Description Language (WSDL), discovered through Universal Description, Discovery and Integration (UDDI) and communicate by the Simple Object Access Protocol (SOAP). Such a divination has never been fully accomplished yet. Although it was criticized that WSDL only has a syntactic definition of web services, but was not semantic, prior initiatives in semantic web services did not establish a correct methodology to resolve the problem. This paper examines the distinction and relationship between the syntactic and semantic definitions for web services that characterize different purposes in service computation. Further, this paper proposes that the semantics of web service are neutral and independent from the service interface definition, data types and platform. Such a conclusion can be a universal law in software engineering and service computing. Several use cases in the GIScience application are examined in this paper, while the formalization of geospatial services needs to be constructed by the GIScience community towards a comprehensive ontology of the conceptual definitions and relationships for geospatial computation. Advancements in semantic web services research will happen in domain science applications.

The number of web services available on the Internet has grown rapidly. Service consumers face a hard decision over which service to choose among the available ones. Security holds a key after various vulnerabilities have been exploited by attackers on number of notable web services. This paper carries out a survey on how security has been expressed and promised for web services, through both the Web Service Description Language and Service Level Agreements. It reviews existing technologies used for comparing individual web services, as well as for service compositions. Taking security into account further complicates the already difficult process of choosing the right service. The paper reveals that despite existing efforts, a quantitative solution needs to be established urgently in order to help service consumers to choose the most secure service for them to use.

The development, registration, discovery, and invocation of quality Web services are vital for the successful implementation of applications using Web services. Considerable research focuses on quality for Web services. Unfortunately, current research on Quality of Service (QoS) for Web services is concentrated on service users and the implementation stage. This research highlights the importance of incorporating QoS at the design and development stages; the authors propose the introduction of QoS at the same time as functional requirements. However, Web Service Description Language (WSDL) describes the functional elements of a Web service, and QoS is significant for this description. Therefore, the authors propose an extension to the WSDL through a generic QoS metamodel, incorporating QoS specifications into the functionalities. This paper begins by defining the required QoS specifications for the development of quality Web services and explores the potential of the Unified Modeling Language as a technique and notation to specify QoS. To properly integrate QoS in the design, the authors propose extensions to the existing UML QoS profile. The paper concludes with the evaluation of the proposed framework and summarises its advantages.

Web service technologies are becoming increasingly important for integrating systems and services. There is much activity and interest around standardization and usage of Web service technologies. Contemporary Web services are described in the Web Service Description Language (WSDL). However, WSDL documents can be difficult to understand for service developers. This article recommends a model-driven process for Web service development combining the graphical modeling language UML with WSDL. The Unified Modeling Language (UML) is developed by Object Management Group. In the proposed process, Web service descriptions (in WDSL) are converted to UML; their UML models are integrated to form composite Web services; and then the new Web service descriptions are exported. The main contribution of this article is a “pure UML” modeling strategy supported by implementation of two-way conversion rules between the UML models and the WSDL documents.

In this chapter, we provide an overview of the Web services technology, together with the set of standard specifications for Web services transactions. The core components of the Web services technology include eXtensible Markup Language (XML), HyperText Transfer Protocol (HTTP), Simple Object Access Protocol (SOAP), and Web Services Description Language (WSDL). Both SOAP and WSDL are based on XML. All these protocols and languages have the characteristic of strong extensibility, which lays a solid foundation for the success of the Web services technology. Due to the extensibility design, the protocols specified in the Web services transactions standards can be plugged into the Web services core seamlessly to provide the additional coordination needed for business transactions. Furthermore, we point out the need to protect the business transactions from the hardware failures and malicious faults, and for more robust coordination for Web services transactions.

Spatial Data Infrastructures often maintain directories of public geospatial Web Services built from Web services listed in their registries. However, registry data may be stale and incomplete because their maintenance depends on service owners. A solution is to back the registry with an active directory, or index, that lists Web services found by a Web crawler focused on geospatial Web services. The problem of the identification of the geospatial nature of a Web service appears when such crawler finds a service described in the Web Services Description Language (WSDL). This paper presents two components required to build an active directory: a crawler focused on Open Geospatial Consortium and WSDL-based Web services, and an unsupervised classifier of geospatial Web services described in WSDL.

Chapter {5} - WSDL

Web Services Description Language (WSDL) allows a structured way to standardize the description of Web Services, exploiting XML for the exchange of structured information. Nevertheless XML supports little interoperability between services, expected when WSDL documents have to be combined. In this context, the Semantic Web has become a promising research field. Semantic Models (e.g. RDF or OWL) allow knowledge from many different sources to be easily combined so that unexpected data connections can be used. In this paper we provide a description of WSDL documents into a metamodel representation of Semantic Models. It allows interoperability at different levels of abstraction. A Datalog rule based system queries both service description and associated semantic annotations. Such system is built on top of traditional database technology to guarantee an efficient management of Semantic Web Services Descriptions. Finally we present experiments on a real dataset to test the feasibility of the modeling approach.

There are several tools and techniques developed over the past decade for detecting duplicated code in software. However, there exists a class of languages for which clone detection is ill-suited. We discovered one of these languages when we attempted to use clone detection to find similar web service operations in service descriptions written in the Web Service Description Language (WSDL). WSDL is structured in such a way that identifying units for comparison becomes a challenge. WSDL service descriptions contain specifications of one or more operations that are divided into pieces and intermingled throughout the description. In this paper, we describe a method of reorganizing them in order to leverage clone detection technology to identify similar services. We introduce the idea of contextual clones -- clones that can only be found by augmenting code fragments with related information referenced by the fragment to give it context. We demonstrate this idea for WSDL and propose other languages and situations for which contextual clones may be of interest.

Service oriented architecture is a glue that allows web applications to work in collaboration. It has become a driving force for the service-oriented computing (SOC) paradigm. In heterogeneous environments the SOC paradigm uses web services as the basic building block to support low costs as well as easy and rapid composition of distributed applications. A web service exposes its interfaces using the Web Service Description Language (WSDL). A central repository called universal description, discovery and integration (UDDI) is used by service providers to publish and register their web services. UDDI registries are used by web service consumers to locate the web services they require and metadata associated with them. Manually analyzing WSDL documents is the best approach, but also most expensive. Work has been done on employing various approaches to automate the classification of web services. However, previous research has focused on using a single technique for classification. This research paper focuses on the classification of web services using a majority vote based classifier ensemble technique. The ensemble model overcomes the limitations of conventional techniques by employing the ensemble of three heterogeneous classifiers: Naive Bayes, decision tree (J48), and Support Vector Machines. We applied tenfold cross-validation to test the efficiency of the model on a publicly available dataset consisting of 3738 real world web services categorized into 5 fields, which yielded an average accuracy of 92 %. The high accuracy is owed to two main factors, i.e., enhanced pre-processing with focused feature selection, and majority based ensemble classification.

There has been a great deal of hype in the business world concerning Web services. You have probably heard all about them recently, you may have read an article about them. The truth is that I have heard as many different explanations for what a Web service is as people I have heard try to explain what it is. This chapter gives you a solid definition (at least, my version) of what a Web service is and a practical overview of how to implement one. This chapter covers how to create a Web service and how to incorporate the code that you already created for the rest of the NorthwindTraders application. It also covers how to access that Web service from another Windows forms application. You will also see you how to create classes based on a Web service using the Web Service Description Language (WSDL) utility that ships with.NET. This chapter does not cover Web service security, which is an extremely large topic, or the many competing standards and organizations pushing for those standards.

Web service architectures have gained popularity in recent years within the scientific grid research community. One reason for this is that web services allow software and services from various organizations to be combined easily to provide integrated and distributed applications. However, most applications developed and used by scientific communities are not web-service-oriented, and there is a growing need to integrate them into grid applications based on service-oriented architectures. In this paper, we describe a framework that allows scientists to provide a web service interface to their existing applications as web services without having to write extra code or modify their applications in any way. In addition, application providers do not need to be experts in web services standards, such as Web Services Description Language, Web Services Addressing, Web Services Security, or secure authorization, because the framework automatically generates these details. The framework also enables users to discover these application services, interact with them, and compose scientific workflows from the convenience of a grid portal.

In this paper we evaluate the use of case-based classification to resolve a number of questions related to information sharing in the context of an Integrated Web services Brokering System (IWB). We are developing the IWB to independently decompose and analyze ad hoc Web services interface descriptions in order to identify Web services of interest. Our approach is to have the IWB cache information about each service in order to support an autonomous mediation process. In this mediation process, the IWB independently matches the user's data request to the correct method within the appropriate Web service, translates the user's request to the correct syntax and structure of the Web service request, dynamically invokes the method on the service, and translates the Web service response. We use casebased classification as a means of automating the IWB's analysis of relevant services and operations. Case-based classification retrieves and reuses decisions based on training data. We use sample Web Service Description Language (WSDL) files and schema from actual Web services as training data in our approach and do not require the service to pre-deploy an OWL-S ontology. We present our evaluation of this approach and performance ratings in the context of meteorological and oceanographic (MetOc) Web services as it relates to the IWB.

Web services technology is the most common implementation of service oriented architecture. Web services are based on open technologies such as eXtensible Markup Language (XML) and offer a distributed approach for the integration of heterogeneous applications across the internet. The process of combining web services functionalities into one composite service is called web services composition. To perform this task, several languages such as Business Process Execution Language (BPEL), Web Services Flow Language (WSFL) and Web Service Choreography Interface (WSCI) have emerged. These languages are based on programming concepts and neglect the specification step which is very important in any software development process. In this paper, we address the formal specification of web services descriptions and the modelling of their composition using the model driven engineering principles. To this end, we propose a domain specific language (DSL) called S-GNet. The proposed DSL introduces new modelling elements which make it well adapted to the web services characteristics. We also propose a graph grammar which transforms Web Services Description Language (WSDL) descriptions into their equivalent S-GNet specifications. This grammar is integrated within an S-GNet modelling tool.