Semantic web services and its challenges
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Semantic web services and its challenges Semantic web services and its challenges Document Transcript

  • International Journal of Computer and Technology (IJCET), ISSN 0976 – 6367(Print),International Journal of Computer Engineering EngineeringISSN 0976 – 6375(Online) Volume 1, Number 2, Sep - Oct (2010), © IAEMEand Technology (IJCET), ISSN 0976 – 6367(Print)ISSN 0976 – 6375(Online) Volume 1 IJCETNumber 2, Sep - Oct (2010), pp. 26-37 ©IAEME© IAEME, http://www.iaeme.com/ijcet.html SEMANTIC WEB SERVICES AND ITS CHALLENGES Ms. A. Suganthy Assistant Professor Department of Computer Science and Engineering Perunthalaivar Kamarajar Institute of Engg. & Tech Karaikal, E-mail:asugan@gmail.com G.S.Sumithra Department of Computer Science and Engineering Perunthalaivar Kamarajar Institute of Engg. & Tech Karaikal, E-mail: teju_tiny@yahoo.co.in J.Hindusha Department of Computer Science and Engineering Perunthalaivar Kamarajar Institute of Engg. & Tech Karaikal, E-mail:hindu.hindusha@gmail.com A.Gayathri Department of Computer Science and Engineering Perunthalaivar Kamarajar Institute of Engg. & Tech Karaikal, E-mail: ggayathri.pkiet@gmail.com S.Girija Department of Computer Science and Engineering Perunthalaivar Kamarajar Institute of Engg. & Tech Karaikal, E-mail:girija.siva89@gmail.comABSTRACT Semantic web technology has drawn a considerable attention of the researchers inthe field of distributed information systems, artificial intelligence and so on. Researchersare taking interest to make use of semantic web technology as a central component oftheir software constructions. This paper gives an overview of Semantic web and web services, semantic webtechnologies, semantic web architecture, semantic web approaches and key challenges.Keywords – Ontology; Semantic Web services; Web services 26
  • International Journal of Computer Engineering and Technology (IJCET), ISSN 0976 – 6367(Print),ISSN 0976 – 6375(Online) Volume 1, Number 2, Sep - Oct (2010), © IAEMEI.INTRODUCTION It is obvious in modern computing. Semantic web services shares the documentsacross the heterogeneous and global networks. It is a cooperative convergence of thesemantic web and web services. Semantic web deals about ontologies, logic, inferenceand software agents. Web services are an infrastructure for developing the distributedapplications. Semantic Web Services are web services which have been marked andannotated with machine-interpretable semantic markup in the form of ontologies. Onedefinition is the augmentation of descriptions through semantic web annotations, tofacilitate the higher automation of service discovery, composition, invocation andmonitoring in an open, unregulated, and often chaotic environment. [10]. Section2 discusses about the web services and the semantic webs. Section3describes the technologies used in semantic web services. Section4 and section 5 discussabout semantic web architecture and approaches. Section 6 describe about semantic webchallenges.II.WEB SERVICES AND SEMANTIC WEBThis section discusses about Web Services and architecture of Web Services.1. Web Services The term Web services describes a standardized way of integrating Web-basedapplications using the XML, SOAP, WSDL and UDDI open standards over an Internetprotocol. XML is used to tag the data, SOAP is used to transfer the data, WSDL is usedfor describing the services available and UDDI is used for listing what services areavailable. Web services are used primarily as a means for businesses to communicatewith each other and with clients, Web services allows organizations to communicate datawithout intimate knowledge of each others IT systems behind the firewall [1]. Web services allow different applications from different sources to communicatewith each other without time-consuming custom coding, and because all communicationis in XML, Web services are not tied to any one operating system or programminglanguage. For example, Java can talk with Perl; Windows applications can talk withUNIX applications. [1] 27
  • International Journal of Computer Engineering and Technology (IJCET), ISSN 0976 – 6367(Print),ISSN 0976 – 6375(Online) Volume 1, Number 2, Sep - Oct (2010), © IAEME The figure1 shows the basic architecture of Web Services. As illustrated in figure1, the major components in the Web service architecture are service provider, servicerequester and service broker. This Figure1 shows that service providers publish their service(s) with the registryrepository of a service broker. Then, a service requestor initiates a search for a service bycontacting the service broker and searching the registry repository for services that meetspecific search criteria. Figure 1 Web service architecture The broker returns a list of services along with details of the associated providerfor each service. Subsequently, the service requestor binds with a selected serviceprovider(s) based on the provided details of registry repository and consumes them. In thementioned scenario, there are series of standards and protocols which enablecommunication, description, publication and discovery of Web services.[1]2. Semantic Web Semantic Web is a group of methods and technologies to allow machines tounderstand the meaning or "semantics" of information on the World Wide Web. Theterm was coined by World Wide Web Consortium (W3C) director Tim Berners-Lee.According to the original vision, the availability of machine-readable metadata wouldenable automated agents and other software to access the Web more intelligently. Theagents would be able to perform tasks automatically and locate related information onbehalf of the user. Semantic web researchers have proposed to augment web services with asemantic description of their functionality in order to facilitate their discovery andintegration. The combination of web services with semantic web technology is referred asSemantic Web Services. [11] 28
  • International Journal of Computer Engineering and Technology (IJCET), ISSN 0976 – 6367(Print),ISSN 0976 – 6375(Online) Volume 1, Number 2, Sep - Oct (2010), © IAEME While the term "Semantic Web" is not formally defined it is mainly used todescribe the model and technologies proposed by the W3C. These technologies includethe Resource Description Framework (RDF), a variety of data interchange formats (e.g.RDF/XML-eXtensible Markup Language , N3, Turtle, N-Triples), and notations such asRDF Schema (RDFS) and the Web Ontology Language (OWL), all of which are intendedto provide a formal description of concepts, terms, and relationships within a givenknowledge domain. Many of the technologies proposed by the W3C already exist and are used invarious projects. The Semantic Web as a global vision, however, has remained largelyunrealized and its critics have questioned the feasibility of the approach. The semantic web provides the ability to add semantics to web services. First wehave OWL and its predecessor DAML+OIL (Ontology Inference Layer), both of whichare XML languages for representing ontology’s in the web. These technologies are usedto build upon the existing web services technologies to create semantic web services. [2].III. SEMANTIC WEB TECHNOLOGIES Various technologies are used in Semantic Web Services. The major SemanticWeb Technologies that are described in this section are WSDL, OIL, SOAP, UDDI.1. WSDL (Web Services Definition Language)It is an XML based References language for describing web services. • Interfaces to all publicly available functions • Data types for all message requests and message responses Binding to the transport protocol to be used • Addresses for locating the specified services2. SOAP (Simple Object Access Protocol) It is a XML protocol web service communication and invocation. The Simple Object Access Protocol (SOAP) is a lightweight, XML-basedprotocol for exchanging information in a decentralized, distributed environment. SOAPsupports different styles of information exchange, including: Remote Procedure Call style(RPC) and Message-oriented exchange. RPC style information exchange allows forrequest-response processing, where an endpoint receives a procedure-oriented message 29
  • International Journal of Computer Engineering and Technology (IJCET), ISSN 0976 – 6367(Print),ISSN 0976 – 6375(Online) Volume 1, Number 2, Sep - Oct (2010), © IAEMEand replies with a correlated response message. Message-oriented information exchangesupports organizations and applications that need to exchange business or other types ofdocuments where a message is sent but the sender may not expect or wait for animmediate response.3. UDDI (Universal Description, Discovery, and Integration) Universal Description, Discovery, and Integration (UDDI) registry is a collectionof information on all the registered Web services. It enables dynamically discoveringWeb Services providers. UDDI is a free public registry - vendors publish their Webservices and consumers search for appropriate Web services. It has three components: UDDI is relatively lightweight, and contains enough information to direct users toResources hosted outside of it. It uses XML to represent its contents.4. OIL (Ontology Inference Layer) OIL can be regarded as an ontology infrastructure for the Semantic web. It isbased on concepts developed in Description Logic (DL) and frame-based systems and iscompatible with RDFS.IV.SEMANTIC WEB ARCHITECTURE The architecture of semantic web is illustrated in the figure below: Figure 2 Semantic web architecture 30
  • International Journal of Computer Engineering and Technology (IJCET), ISSN 0976 – 6367(Print),ISSN 0976 – 6375(Online) Volume 1, Number 2, Sep - Oct (2010), © IAEME The first layer, URI and Unicode, follows the important features of the existingWWW. Unicode is a standard of encoding international character sets and it allows thatall human languages can be used (written and read) on the web using one standardizedform. Uniform Resource Identifier (URI) is a string of a standardized form that allows touniquely identify resources (e.g., documents). A subset of URI is Uniform Resource Locator (URL), which contains accessmechanism and a (network) location of a document - such as http://www.example.org/.Another subset of URI is URN that allows to identify a resource without implying itslocation and means of dereferencing it - an example is urn:isbn:0-123-45678-9. Theusage of URI is important for a distributed internet system as it provides understandableidentification of all resources. An international variant to URI is InternationalizedResource Identifier (IRI) that allows usage of Unicode characters in identifier and forwhich a mapping to URI is defined. In the rest of this text, whenever URI is used, IRI canbe used as well as a more general concept. Extensible Markup Language (XML) layer with XML namespace and XMLschema definitions makes sure that there is a common syntax used in the semantic web.XML is a general purpose markup language for documents containing structuredinformation. An XML document contains elements that can be nested and that may haveattributes and content. XML namespaces allows to specify different markup vocabulariesin one XML document. XML schema serves for expressing schema of a particular set ofXML documents. A core data representation format for semantic web is Resource DescriptionFramework (RDF). RDF is a framework for representing information about resources in agraph form. It was primarily intended for representing metadata about WWW resources,such as the title, author, and modification date of a Web page, but it can be used forstoring any other data. It is based on triples subject-predicate-object that form graph ofdata. All data in the semantic web use RDF as the primary representation language. Thenormative syntax for serializing RDF is XML in the RDF/XML form. Formal semanticsof RDF is defined as well. RDF itself serves as a description of a graph formed by triples. Anyone can definevocabulary of terms used for more detailed description. To allow standardized description 31
  • International Journal of Computer Engineering and Technology (IJCET), ISSN 0976 – 6367(Print),ISSN 0976 – 6375(Online) Volume 1, Number 2, Sep - Oct (2010), © IAEMEof taxonomies and other ontological constructs, a RDF Schema (RDFS) was createdtogether with its formal semantics within RDF. RDFS can be used to describe taxonomiesof classes and properties and use them to create lightweight ontologies. The OWL is a language derived from description logics, and offers moreconstructs over RDFS. It is syntactically embedded into RDF, so like RDFS, it providesadditional standardized vocabulary. OWL comes in three species - OWL Lite fortaxonomies and simple constrains, OWL DL for full description logic support, and OWLFull for maximum expressiveness and syntactic freedom of RDF. Since OWL is based ondescription logic, it is not surprising that a formal semantics is defined for this language. RDFS and OWL have semantics defined and this semantics can be used forreasoning within ontologies and knowledge bases described using these languages. Toprovide rules beyond the constructs available from these languages, rule languages arebeing standardized for the semantic web as well. Two standards are emerging - RIF andSWRL.V.SEMANTIC WEB APPROACHES Here we discuss about the Semantic Web approaches namely Annotation,Composition, Privacy and Security.1. Annotation Annotation of web services is the fundamental concepts underlying semantic webservices. DAML-S and OWL-S has been the most popular representations of web serviceontology but they are not without flaws, competitors and possible improvements. [2]2. Composition The OWL-S proposal [7] describes composite services thus: “complex orcomposite services are composed of multiple mode primitive services, and may requirean extended interaction or conversation between the requester and the set of services thatare being utilized.” The need for composing services comes from web services.The BPEL4WS is one language which attempts to enable composition of web servicesinto executable processes. In Semantic Web Services composition is performed automatically by the systembased only on declarative descriptions of the task and services. 32
  • International Journal of Computer Engineering and Technology (IJCET), ISSN 0976 – 6367(Print),ISSN 0976 – 6375(Online) Volume 1, Number 2, Sep - Oct (2010), © IAEME3. Privacy and Security Privacy and Security work has mostly taken the form of policy languages withwhich to annotate services. Security information includes encryption and digital signatureinformation about how inputs /outputs will be passed and stored. It also includesinformation about to where information may be sent and for what purpose. Kagal et al. [5] describes policies for authorization and privacy for SWS which“aims to provide security and policy annotations for OWL-S service descriptions”. Denker et al. [3] proposes security ontologies to annotate web services withsecurity information and describes a prototype. Tontietal. [15] compares three languages for policy representation: KaoS,Rei andPonder.V. KEY CHALLENGES The most probable achievements that the SWS research community is expected tomake by 2012, the potential of SWSs with respect to integration architectures and theavailability of real-world studies in which SWS- based integration architectures are used.[ 3] Since 2001, the number of publications devoted to SWSs is constantly growing.Mcllraith et al. (2001) published one of the first scientific articles on SWSs. A GoogleScholar query for SWS-related articles in Six matches for the year 2001. For the years2004 and 2005, Google Scholar lists 189 and 344 articles, respectively. In 2006 the queryresults in 426 matches and in 2007 the query results in 458 publications.[10] Figure 3 described the evolution of the web which consists largely of documentsfor humans to read to a Semantic Web that includes data and information for computersto manipulate. The existing applications have been developed in academic contexts or researchprojects funded by public institutions. Work on Semantic Web languages and standardsprovide a set of metadata to be used, nor do they say anything about how metadata can beobtained [ 3]. Semantic Web provides some languages that express information in a machineprocessable format. This implies that we do still have more expectations from our 33
  • International Journal of Computer Engineering and Technology (IJCET), ISSN 0976 – 6367(Print),ISSN 0976 – 6375(Online) Volume 1, Number 2, Sep - Oct (2010), © IAEMEcomputers today; we would like to take more benefit from their processing power. Thisidea is also one goal of the “Grand Challenges in the Evolution of Information Society”[17]. Figure 3 Berners-Lee Semantic Web The World Wide Web Consortium (W3C) who has been working intensively onSemantic standards, has approved the Resource Definition Framework (RDF) and theOWL Web Ontology Language (OWL) and hence provides a solid base to establishenterprise semantic applications and has implied a significant leverage of the SemanticWeb from a research level to an industry standard for building next generationapplications. Like other technologies, the interest in creating and developing the Semantic Webis motivated by the opportunities it might bring: either it can solve old problems, or it cansolve old problem in a better way. Here, instead of enumerating all the opportunitiesenabled by the Semantic Web, we focus our discussion on the following closely relatedaspects: web-services, agent-based distributed computing, semantics-based web searchengines, and semantics-based digital libraries [13]. Only limited semantics can be derivedfrom the lexical or syntactic content of the web pages. Several systems have been built to overcome these problems based on their ideaof annotating Web pages with special HTML tags to represent semantics, includingSHOE (Simple HTML Ontology Extensions) system.[8]. 34
  • International Journal of Computer Engineering and Technology (IJCET), ISSN 0976 – 6367(Print),ISSN 0976 – 6375(Online) Volume 1, Number 2, Sep - Oct (2010), © IAEME New opportunities impose new challenges. In the following, we focus ourdiscussion on the following challenges that we are facing now: the development ofontologies, and the development of the formal semantics of Semantic Web languages,and the development of trust and proof models.[13]. The goal of the SWS Challenge is todevelop a common understanding of various technologies intended to facilitate theautomation of mediation, choreography and discovery for Web Services using semanticannotations. The intent of this challenge is to explore the trade-offs among existingapproaches. Typically, we only run one surprise problem at a workshop due to resourcerestrictions, but there may be exceptions to this practice. The process is summarized inthe table 1. Date/Time Phase Description Committed participants will receive "Code freeze"(1) Deadline Day 0 instructions and credentials for the credentials distribution Phase 2. "Code freeze" The deadline for existing solution(2) Day 1 submission submissions. Committed participants will gain Surprise problem(3) Day 2 access to the surprise problem announcement description. Day 2 + n - depending The deadline for surprise problem(4) Solution submission upon the problem solution submissions. The surprise problem solutions(5) Next Day Solution verification verification report. Table 1: Surprise problem solution A solution submission should be accompanied with a document clearly stating allchanges that were introduced to the frozen version in order to respond to the surpriseproblem requirements. Further, we may ask at the workshop that participants dynamicallydemonstrate the ability to make minor changes to the surprise problem and get the newcorrect answer [15]. The overall objective of the challenge is to apply Semantic Web techniques inbuilding online end-user applications that integrate, combine and deduce informationneeded to assist users in performing tasks. Intentionally, the challenge does not definespecific task, data set, application domain or technology to be used because the potential 35
  • International Journal of Computer Engineering and Technology (IJCET), ISSN 0976 – 6367(Print),ISSN 0976 – 6375(Online) Volume 1, Number 2, Sep - Oct (2010), © IAEMEapplicability of the Semantic Web is very broad. Instead, a number of minimal criteriahave been defined which allow people to submit a broad range of applications.VI. CONCLUSION Semantic Web Service is an emerging technology for supporting distributedcomputing in the environments like Internet. Research is going on to formulate astandardized architecture for Semantic Web. And the Framework for describing theOntology is also not well defined. There are still many issues to be resolved. TheSemantic Web Technologies are all new and demands its own requirements.VII. REFERENCES 1. Berners-Lee, T, Hendler, James and Miller, E (2002). Integrating Applications on the Semantic Web," Journal of the Institute of Electrical Engineers of Japan, October, 2002. 2. Berners-Lee, Tim; James Hendler and Ora Lassila (May 17, 2001). "The Semantic Web". Scientific American Magazine. Retrieved March 26, 2008. 3. Daniel Bachlechner,Kerstin Fink,”Semantic Web Service Research: Current Challenges and Proximate Achievements” 4. David Brokenshire,Surrey BC V3T 5X3, “A Review of Semantic Web services”. 5. Denker. G., Kagal, L., Finin, T., Paolucci, M., and Sycara,K. security for DAML Web services: Annotation and Matchmaking, Vol. 2870.Jan 2003. 6. Jagadeesh Nandigam, Venkat Ngidivada, Mrunalini Kalavala “Semantic Web Services” 7. Kagal, L, Finin, T., Paolucci, M., Srinivasan,N.Sycara, K., and Denker,G. authorization and Privacy for Semantic Web Services. Intelligent Systems, IEEE (see also IEEE Intelligent Systems and their Applications) 19, 4 (2004). 8. Luke, S., Spector, L., Rager, D. & Hendler, J. (1997). "Ontology-based web agents". In Proceedings of the 1st International Conference on Autonomous Agents, Marina del Rey, California, pp. 59-68 New York, NY: ACM press. 9. Martin, D.,Paolucci, M.,Mcllraith, S.A.,Burstein, M,; McGuinness, D., Parsia, B.; Payne, T., Sabou,M.;Solanki,M.,Srinivasan, N.,Sycara,K. (2004): Bringing 36
  • International Journal of Computer Engineering and Technology (IJCET), ISSN 0976 – 6367(Print),ISSN 0976 – 6375(Online) Volume 1, Number 2, Sep - Oct (2010), © IAEME Semantics to Web Services: the OWL-S approach, Proceedings of the First International Workshop on Semantic Web services and Web Process Composition. 10. Mcllraith, S.A., Son, T. C., Zeng,H. (2001):Semantic Web Services,IEEE Intelligent Systems, 16(2),pp. 46-52. 11. Payne, T., and Lassila, O. Guest Editors Introduction: Semantic Web Services. Intelligent Systems, IEEE (see also IEEE Intelligent Syatems and their Applications) 17, 1 (2002),15 –17. 12. Sabou, Marta. Building Web Service Ontologies. The Dutch Graduate School For information and Knowledge Systems http://Kmi.open.ac.uk/people/marta/papers/thesis.pdf. 13. Shiyong Lu, Ming Dong and Farshad Fotouhi “The Semantic Web: opportunities and challenges for next-generation Web applications”. 14. “Semantic Web Service Challenge: Evaluating Semantic Web Services Mediation, Choreography and Discovery” , sponsored by STI International. 15. STAAB, S.,Van Der Aalst, W,Benjamins,V., Sheth,A., Miller,J., Bussler,C., Maedche,A Fensel,D., abd Gannon,D.Web services,been there, done that, Intelligent Systems, IEEE (see also IEEE Intelligent Syatems and their Applications) 17, 1 (2002),15 –17. 16.Tonti.G.,Bradshaw,J.M.,Jeffers,R.,Montanari,R.,Suri,N., and Uszok, A. Semantic Web Languages for Policy Representation and Reasoning: A Comparison of KaoS, Rei,and Ponder, vol. 2870. Jan. 2003. 17. Wolfgang Wahlster, “Grand Challenges in the Evolution of the Information Society”, November 2004. 18. WWW.dcs.bbk.ac.uk/…/ervices/Architecture.gif. 19. WWW.Wikipedia.com 37