Approaches to Semantic Web Services: An Overview and Comparison

Abstract. The next Web generation promises to deliver Semantic Web Services (SWS); services that are self-described and amenable to automated discovery, composition and invocation. A prerequisite to this, however, is the emergence and evolution of the Semantic Web, which provides the infrastructure for the semantic interoperability of Web Services. Web Services will be augmented with rich formal descriptions of their capabilities, such that they can be utilized by applications or other services without human assistance or highly constrained agreements on interfaces or protocols. Thus, Semantic Web Services have the potential to change the way knowledge and business services are consumed and provided on the Web. In this paper, we survey the state of the art of current enabling technologies for Semantic Web Services. In addition, we characterize the infrastructure of Semantic Web Services along three orthogonal dimensions: activities, architecture and service ontology. Further, we examine and contrast three current approaches to SWS according to the proposed dimensions

Policies for Web Services

Web services are predominantly used to implement service-oriented architectures (SOA). However, there are several areas such as temporal dimensions, real-time, streaming, or efficient and flexible file transfers where web service functionality should be extended. These extensions can, for example, be achieved by using policies. Since there are often alternative solutions to provide functionality (e.g., different protocols can be used to achieve the transfer of data), the WS-Policy standard is especially useful to extend web services with policies. It allows to create policies to generally state the properties under which a service is provided and to explicitly express alternative properties. To extend the functionality of web services, two policies are introduced in this thesis: the Temporal Policy and the Communication Policy. The temporal policy is the foundation for adding temporal dimensions to a WS-Policy. The temporal policy itself is not a WS-Policy but an independent policy language that describes temporal dimensions of and dependencies between temporal policies and WS-Policies. Switching of protocol dependencies, pricing of services, quality of service, and security are example areas for using a temporal policy. To describe protocol dependencies of a service for streaming, real-time and file transfers, a communication policy can be utilized. The communication policy is a concrete WS-Policy. With the communication policy, a service can expose the protocols it depends on for a communication after its invocation. Thus, a web service client knows the protocols required to support a communication with the service. Therefore, it is possible to evaluate beforehand whether an invocation of a service is reasonable. On top of the newly introduced policies, novel mechanisms and tools are provided to alleviate service use and enable flexible and efficient data handling. Furthermore, the involvement of the end user in the development process can be achieved more easily. The Flex-SwA architecture, the first component in this thesis based on the newly introduced policies, implements the actual file transfers and streaming protocols that are described as dependencies in a communication policy. Several communication patterns support the flexible handling of the communication. A reference concept enables seamless message forwarding with reduced data movement. Based on the Flex-SwA implementation and the communication policy, it is possible to improve usability - especially in the area of service-oriented Grids - by integrating data transfers into an automatically generated web and Grid service client. The Web and Grid Service Browser is introduced in this thesis as such a generic client. It provides a familiar environment for using services by offering the client generation as part of the browser. Data transfers are directly integrated into service invocation without having to perform data transmissions explicitly. For multimedia MIME types, special plugins allow the consumption of multimedia data. To enable an end user to build applications that also leverage high performance computing resources, the Service-enabled Mashup Editor is presented that lets the user combine popular web applications with web and Grid services. Again, the communication policy provides descriptive means for file transfers and Flex-SwAs reference concept is used for data exchange. To show the applicability of these novel concepts, several use cases from the area of multimedia processing have been selected. Based on the temporal policy, the communication policy, Flex-SwA, the Web and Grid Service Browser, and the Service-enabled Mashup Editor, the development of a scalable service-oriented multimedia architecture is presented. The multimedia SOA offers, among others, a face detection workflow, a video-on-demand service, and an audio resynthesis service. More precisely, a video-on-demand service describes its dependency on a multicast protocol by using a communication policy. A temporal policy is then used to perform the description of a protocol switch from one multicast protocol to another one by changing the communication policy at the end of its validity period. The Service-enabled Mashup Editor is used as a client for the new multicast protocol after the multicast protocol has been switched. To stream single frames from a frame decoder service to a face detection service (which are both part of the face detection workflow) and to transfer audio files with the different Flex-SwA communication patterns to an audio resynthesis service, Flex-SwA is used. The invocation of the face detection workflow and the audio resynthesis service is realized with the Web and Grid Service Browser

DPWSim: A Devices Profile for Web Services (DPWS) Simulator

The Devices Profile for Web Services (DPWS) standard enables the use of Web services for resource-constrained devices, main components of the Internet of Things (IoT). DPWS can power the next generation of IoT applications connecting millions of networked devices and services on the Web. This article presents a simulator, called DPWSim, to support the use of this technology. DPWSim featuring secure messaging, dynamic discovery, service description, service invocation, and publishsubscribe eventing can be used to prototype, develop, and test products in terms of DPWS communication protocols. It can also support the collaboration between manufacturers, developers, and designers during the new product development process

A conceptual architecture for semantic web services development and deployment

Several extensions of the Web Services Framework (WSF) have been proposed. The combination with Semantic Web technologies introduces a notion of semantics, which can enhance scalability through automation. Service composition to processes is an equally important issue. Ontology technology – the core of the Semantic Web – can be the central building block of an extension endeavour. We present a conceptual architecture for ontology-based Web service development and deployment. The development of service-based software systems within the WSF is gaining increasing importance. We show how ontologies can integrate models, languages, infrastructure, and activities within this architecture to support reuse and composition of semantic Web services

SCC: A Service Centered Calculus

We seek for a small set of primitives that might serve as a basis for formalising and programming service oriented applications over global computers. As an outcome of this study we introduce here SCC, a process calculus that features explicit notions of service definition, service invocation and session handling. Our proposal has been influenced by Orc, a programming model for structured orchestration of services, but the SCC’s session handling mechanism allows for the definition of structured interaction protocols, more complex than the basic request-response provided by Orc. We present syntax and operational semantics of SCC and a number of simple but nontrivial programming examples that demonstrate flexibility of the chosen set of primitives. A few encodings are also provided to relate our proposal with existing ones

MAPI: towards the integrated exploitation of bioinformatics Web Services

<p>Abstract</p> <p>Background</p> <p>Bioinformatics is commonly featured as a well assorted list of available web resources. Although diversity of services is positive in general, the proliferation of tools, their dispersion and heterogeneity complicate the integrated exploitation of such data processing capacity.</p> <p>Results</p> <p>To facilitate the construction of software clients and make integrated use of this variety of tools, we present a modular programmatic application interface (<it>MAPI</it>) that provides the necessary functionality for uniform representation of Web Services metadata descriptors including their management and invocation protocols of the services which they represent. This document describes the main functionality of the framework and how it can be used to facilitate the deployment of new software under a unified structure of bioinformatics Web Services. A notable feature of <it>MAPI </it>is the modular organization of the functionality into different modules associated with specific tasks. This means that only the modules needed for the client have to be installed, and that the module functionality can be extended without the need for re-writing the software client.</p> <p>Conclusions</p> <p>The potential utility and versatility of the software library has been demonstrated by the implementation of several currently available clients that cover different aspects of integrated data processing, ranging from service discovery to service invocation with advanced features such as workflows composition and asynchronous services calls to multiple types of Web Services including those registered in repositories (e.g. <it>GRID</it>-based, SOAP, <it>BioMOBY</it>, <it>R-bioconductor</it>, and others).</p

Implementing Session Centered Calculi

Recently, specific attention has been devoted to the development of service oriented process calculi. Besides the foundational aspects, it is also interesting to have prototype implementations for them in order to assess usability and to minimize the gap between theory and practice. Typically, these implementations are done in Java taking advantage of its mechanisms supporting network applications. However, most of the recurrent features of service oriented applications are re-implemented from scratch. In this paper we show how to implement a service oriented calculus, CaSPiS (Calculus of Services with Pipelines and Sessions) using the Java framework IMC, where recurrent mechanisms for network applications are already provided. By using the session oriented and pattern matching communication mechanisms provided by IMC, it is relatively simple to implement in Java all CaSPiS abstractions and thus to easily write the implementation in Java of a CaSPiS process

Using semantics for automating the authentication of Web APIs

Recent technology developments in the area of services on the Web are marked by the proliferation of Web applications and APIs. The implementation and evolution of applications based on Web APIs is, however, hampered by the lack of automation that can be achieved with current technologies. Research on semantic Web services is there fore trying to adapt the principles and technologies that were devised for traditional Web services, to deal with this new kind of services. In this paper we show that currently more than 80% of the Web APIs require some form of authentication. Therefore authentication plays a major role for Web API invocation and should not be neglected in the context of mashups and composite data applications. We present a thorough analysis carried out over a body of publicly available APIs that determines the most commonly used authentication approaches. In the light of these results, we propose an ontology for the semantic annotation of Web API authentication information and demonstrate how it can be used to create semantic Web API descriptions. We evaluate the applicability of our approach by providing a prototypical implementation, which uses authentication annotations as the basis for automated service invocation