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  1. 1. A draft of architecture for implementing semantic web enabled web services : A Case Study Neha Garg1 , Sanjay Kumar Malik2, Nupur Prakash3, SAM Rizvi4 1 M.Tech.-IT, VI Semester, University School of Information Technology, GGS Indraprastha University, Delhi 2 University School of Information Technology, GGS Indraprastha University, Delhi 3 University School of Information Technology, GGS Indraprastha University, Delhi 4 Deptt. of Computer Science,Jamia Millia Islamia, New Delhi neha.garg@sap.com1, sdmalik@hotmail.com2, nupurprakash@rediffmail.com3, samsam_rizvi@yahoo.com4 ABSTRACT means Web sites that do not merely provide static information but allow one In the last few years, the amount of to effect some action or change in the information on the World Wide Web world, such as the sale of a product or (WWW) has grown exponentially and the control of a physical device[1]. The searching information on web has become Semantic Web should enable users to an important issue. Semantic Web and Web locate, select, employ, compose, and Services are the main trends for extending monitor Web-based services the existing web, but each of them cannot automatically. Web services are “self- enable web automation alone. contained, self-describing modular applications”. They constitute software The use of Web services on the Web is modules that “describe a collection of expanding rapidly as the need for operations that are network-accessible application-to-application communication through standardized XML messaging”. and interoperability grows. These services provide a standard means of communication The Serious problems in the Web was among different applications involved in Information finding, Information presenting dynamic context-driven extracting, Information representing information to the user. ,Information interpreting and Information maintaining. With the Semantic Web Enabled Web Services introduction of Web Services, we can (SWWS) tend to transform the web from a use the web to its full potential. static collection of information into a distributed system of computation making the content machine-processable and machine-interpretable within the Web. Semantic Web Enabled Web Services will allow the automatic discovery, selection and execution of inter-organization business logic making areas like dynamic supply chain composition a reality. In this paper we make a case study and present a To make use of a Web service, a theoretical draft of architecture for software agent needs a computer- implementing Semantic web enabled web interpretable description of the service, services. and the means by which it is accessed. An important goal for Semantic Web Keywords: Semantic Web, Semantic Web markup languages, then, is to establish a enabled Web Services [SWWS], Web framework within which these Services Definition language [WSDL]. descriptions are made and shared. Current efforts in developing Semantic 1-INTRODUCTION Web Service infrastructures can be characterized Among the most important Web resources Along three orthogonal dimensions: are those that provide services. ``Service'' usage activities, architecture and
  2. 2. service ontology [3]. Usage activities define use are explicitly defined. Formal means the functional requirements, which a refers to the fact that the ontology should framework for Semantic Web Services be machine readable. Shared shows that should support. The architecture of SWS ontology should capture consensual describes the components needed for knowledge accepted by the communities accomplishing the activities defined for [7]. SWS, whereas the service ontology aggregates all concept models related to the The Semantic Web provides the description of a Semantic Web Service [3]. necessary infrastructure for publishing and resolving ontological descriptions of This paper deals with two of the advanced terms and concepts. In addition, it technologies, currently associated with the provides the necessary techniques for Web — Semantic Web and Web services. reasoning about these concepts, as well This paper is structured as follows: In as resolving and mapping between section 1, we provide an overview of ontologies, thus enabling semantic Semantic web and semantic web enabled interoperability of Web Services through web services. In section 2, we present an the identification of semantically similar overview of the Semantic Web and in concepts. particular of those aspects which allow the Semantic Web techniques can enhance specification of semantic description for the current web service architecture. In Web services. Section 3 presents general the longer term, the Semantic Web overview/architecture of Web services. In vision itself becomes more interesting, section 4 we describe the architecture of with Web Services offering an Semantic Web Services. infrastructure on which to build the next generation of deployed multiagent 2-SEMANTIC WEB systems. The Semantic Web is a vision of a new Example: Benefits of ontologies for architecture for the World Wide Web, the hospitals. Hospital Services (HS) is characterized by the association of machine- an organization pioneering the accessible formal semantics with more development and use of specifications traditional Web content. The Semantic that support e-business among all Web’s original motivations were to increase segments of the medical domain. The automation in processing Web based cumulative effort of various teams, information and to improve the individuals, associations, companies, interoperability of Web based information and international organizations and systems [2]. Semantic Web techniques, technology providers, has produced a which consist of applying knowledge fairly complete set of XML-based representation techniques in a distributed specifications for the medical domain. environment, are useful in providing richer The current development of open descriptions of Web resources. specifications messages based on XML, such as the HS schema, to ensure the Ontologies are considered the basic building interoperability between working groups block of the Semantic Web as they allow is not sufficiently expressive to guaranty machine supported data interpretation an automatic exchange and processing of reducing human involvement in data and information. The development of a process integration. suitable ontology for the medical domain is indispensable and will serve as a An ontology is a formal, explicit common language for medical-related specification of a shared conceptualization. terminology and a mechanism for Conceptualization means to an abstract promoting the seamless exchange of model of phenomena in the world by having information across all hospitals. identified the relevant concepts of those The development of such an ontology phenomena. Explicit means that the type of can be used to bring together concepts used, and the constraints on their
  3. 3. autonomous and heterogeneous Web offer specific functionality to users. services, Web processes, applications, data, Web services allow different and components residing in distributed applications from different sources to environments. Semantics allow rich communicate with each other descriptions of Web services and Web without time-consuming custom processes that can be used by computers for coding, and because all automatic processing in various medical related applications. communication is in XML, Web services are not tied to any one For the medical domain, the simplest form operating system or programming to construct an ontology is to retrieve rich language. For example, Java can talk semantic interrelationships from the data with Perl, Windows applications can and terminology present in the XML-based talk with UNIX applications. Web OTA specifications already implemented services do not require the use of and available to organizations. This browsers or HTML. procedure is illustrated in Figure 4. Web services are sometimes called application services. The common usage scenario for Web 3-WEB SERVICES services (figure 2) can be defined by three phases; Publish, Find, and Bind The term Web services describes a [3]; and three entities: the requester, standardized way of integrating Web- which invokes services; the provider based applications using the XML, SOAP, which responds to requests; and the WSDL and UDDI open standards over an registry where services can be published Internet protocol backbone. XML is used or advertised. A provider publishes a to tag the data, SOAP is used to transfer description of a service it provides to a the data, WSDL is used for describing service registry. This description (or the services available and UDDI is used advertisement) includes a profile on the for listing what services are available. provider of the service (e.g. company Web services are used primarily as a name and address); a profile about the service itself (e.g. name, category); and means for businesses to communicate the URL of its service interface with each other and with clients, Web definition (i.e. WSDL description).When services allow organizations to communicate a developer realizes a need for a new data without intimate knowledge of each service, he finds the desired service other's IT systems behind the firewall. either by constructing a query, or Unlike traditional client/server models, such browsing the registry. The developer as a Web server/Web page system, Web then interprets the meaning of the services do not provide the user with a GUI. interface description and binds to the Web services instead share business logic, discovered service within the application data and processes through a programmatic they are developing. This application is interface across a network. The applications known as the requester. At this point, interface, not the users. Developers can then the requester can automatically invoke add the Web service to a GUI (such as a the discovered service using Web Web page or an executable program) to
  4. 4. service communication protocols (i.e. knowledge representation of linked SOAP) [2]. data. The W3C has developed a new generation of open standard markup XML schema gives the framework for both languages that are now poised to defining the Web Services Standards, and unleash the power, flexibility and, data types etc that are exchanged between above all, logic of the next services. SOAP is XML-data transport protocol, used for data exchange over web- generation of the Web, and open the based communications protocols. SOAP door to the next generation of Web messages can carry an XML payload Services. Currently, Web Services defined using XML-Schema, thus ensuring a that use the .NET and J2EE frameworks consistent interpretation of data items are struggling to expand against the between different services. limitations of existing Web architecture and conflicting WSDL is an XML format for describing proprietary standards. network services as a set of endpoints operating on messages containing either Semantic Web services will allow the document-oriented or procedure-oriented semi-automatic and automatic information. WSDL is extensible to allow description of endpoints and their messages annotation, advertisement, discovery, regardless of what message formats or selection, composition, and execution network protocols are used to communicate. of inter-organization business logic, making the Internet become a global The semantics of a Web service is the shared common platform where expectation about the behavior of the organizations and individuals service, in particular in response to communicate among each other to messages that are sent to it. In effect, this is carry out various commer-cial the "contract" between the requester entity activities and to provide value-added and the provider entity regarding the services. purpose and consequences of the interaction. Although this contract represents the overall agreement between the requester entity and Semantic Web Services is an the provider entity on how and why their addition of Semantic Web respective agents will interact. Technology and Web Services technology. Semantic Web Services = Semantic Web Technology +Web Services Technology By Using steps defined in figure 3[5] a requester entity might engage and use a Web service. 4-SEMANTIC WEB SERVICE ARCHITECTURE The objective of the Semantic Web A service is a callable routine that is Services Architecture is to provide a made available over a network. A
  5. 5. service exposes an interface contract, which power than graph-oriented control flow, defines both the behavior of the service, and but on the other side it is simpler and the messages it accepts and returns. more effective approach for process engineers because it is less error-prone. Interfaces are often published in public The modeling constructs assure per registries or directories where they are definition that the process definition at categorized based on different services the end is well formed. Graph-oriented offered, just as businesses and their phone control flow requires some verification numbers are listed in a phone book's yellow capabilities to be supported by modeling pages. Clients (service consumers) can look tools. However, using only the block- up a particular service by dynamically oriented approach may be too restrictive. querying for services based on various It was a design decision to allow both categorization features. This process is approaches and leave up to process referred to as the dynamic discovery of engineers to use preferred one. services. The language provides a set of primitive Clients consume services via messages. and structured activities [6]. The set of Because interface contracts are independent primitive activities includes Web of platform and language, messages are services interaction activities. The set of typically constructed using XML documents structured activities includes activities that conform to XML schema. known from other programming languages, such as ordered sequence of Web services typically start and end with activities, iterations, conditional paths, considerations of basic formatting of parallel execution of multiple activities, messages, delivery options, static interfaces and alternative exclusive paths. The describing messages that the service can language also allows handling messages consume and/or produce, services metadata, that may be received asynchronously transactional properties, reliability and within a certain time frame. security.Behind services there are processes, The language provides a mechanism to which could also be hard-coded, driving identify the target service dynamically, those services and making them long based on values in incoming messages running entities[6]. In that case services can [6]. The set of services participating in a offer alternative operations to service process as partners can vary during the consumers and must comply with the execution of the process itself. underlying processes. Also, building new The language provides a mechanism to applications by composing existing Web partially “undo” a given set of services is a new aspect of a Service- activities[6].Web services are considered Oriented Architecture (SOA). to be autonomous entities and their relationships with other Web services The Web Services Business Process participating in the same business Execution Language (WS-BPEL, process are loose. This requires a BPEL4WS or BPEL) is considered as one of different model for error handling and the key building blocks of SOA. transactional behavior within the process context. The language provides a means The BPEL language introduces the features to explicitly define which parts of the needed to specify Web services-based process must be managed in business processes. It is an XML-based transactional way and which activities language which is built on top of WSDL, must be performed to partially undo the XPath , and XML Schema. outcome of a set of activities. The language provides a mechanism to The language uses both block-oriented and identify the target process instance [6]. graph-oriented control flows [6]. Block- A service can be engaged in multiple oriented control flow could be understood as conversations in parallel. The language a special form of graph-oriented control introduces the concept of correlation flow. On one side it has less expressive which describes values that must be
  6. 6. carried in messages to identify the correct choice is to design a loosely coupled process instance. system based on services. These The language follows the idea of building services are backed by open Web services specifications in a composable standards, so any business partner and modular way [6]. It is built over the can execute them. specifications which are considered to be the core of the XML technology and Web services stack. The various components interacting The language introduces the same concepts in the SOA framework are listed for both executable processes and below. It's a typical MVC framework observable behavior of Web services [6]. [4]. With this way it is easier to build executable •Client: The user interacts with completions of an abstract process, which various applications via the web provides the observable behavior of a Web browsers that works as clients for the service. A valid executable completion of an application. abstract process is an executable BPEL •Application controller: It takes processes that follows the same order care of initialization and delegates concerning the interactions with a particular requests and responses to the request partner or a set of partners as the abstract process it implements. processor. BPEL abstract processes complement •Request processor: This is a Java abstract WSDL interfaces and the UDDI class that preprocesses requests by model. They define dependencies between invoking the corresponding request service operations in the context of a handlers to carry out the required message exchange [6]. processing. This invocation is modeled as a command pattern. 4.1. Web Services in an SOA •Request handlers: Request handlers carry out specific request activities, Web services are built on top of open like interacting with services for standards and platform-independent adding or retrieving information protocols. A web service uses SOAP (an from various enterprise information XML-based protocol) over HTTP for systems (EISs). communication between service providers •Business locators: These are and consumers.[4] Services are exposed as interfaces defined by WSDL (Web Service responsible for hiding the complexity Definition Language), whose semantics are of looking up services. defined in XML. UDDI is used for •Session Facades: These provide a interacting with services. simplified view of a complex object by aggregating methods from 4.2. Designing Your SOA/Web multiple systems or services. Session Services Framework facades are wrappers around the EJB Consider the example of a corporation Web services methods. where various systems—such as those •EJB Web services: With the EJB 1.4 for billing, finance, and invoicing—need specification, web services endpoints to interact with each other. In addition, can be modeled as stateless session some of these applications need to be beans. •Data access interfaces: These access exposed to the outside world so that the EIS by using various techniques, like various business partners can interact EJB-CMP, JDO, DAO, and various with them. We also need to design a persistence technologies; the access web-based solution for various technique used depends on interface applications, such as the various data requirements and the volume of data to entry operations for entering invoices or be fetched, inserted, or updated. This finding the status of bills. The best layer is responsible for interacting with
  7. 7. the EIS and returning data back to are based on different logic and ontology corresponding EJB Web service methods in frameworks. the format that those methods expect. •MQSeries/JCA/CCF:Existing mainframe- Summarizing, Semantic Web Services based services can be exposed as web are an emerging area of research and services, thus revealing them to the outside currently all the supporting technologies world. Web service clients interact with EJB are still far from the final product. There web services using the HTTP-based SOAP are technologies available for creating protocol. The EJB methods post requests to distributed applications which rely on an MQSeries queue via the JMS protocol. the execution of Web services deployed The MQSeries server on the mainframe end on the WWW; however, these executes the corresponding COBOL-based technologies require a human user in the programs that provide the logic necessary loop for selecting services available in for interacting with back-end systems like registries. Semantic Web technology can IMS DC. These programs then post the be utilized to do the markup and response back to the queue, which in turn is reasoning of Web service capabilities. retrieved by the application logic and posted back to the EJB calls [4]. There are still a number of issues concerning Semantic Web Services 4.3. Exposing Services to the Outside being investigated in a number of World initiatives. These issues range from For exposing services to external users, we service composition to service trust and need some kind of security constraints that will have the attention of industry and make sure that only authorized users can academia for the next few years. access the services. One way to do this is to provide an additional web service layer that filters out forbidden web service requests 7. REFERENCES and supplies logging and security constraints. This filter should be capable of 1. providing a facility to expose to each client S , W3C Member Submission 22 only the subset of services authorized for November 2004, “OWL-S: Semantic that client. Markup for Web Services”. For Exposing Web Sevices to the External 2. Terry Payne and Ora Lassila Clients we need Extenal Clients, Corporate “Semantic Web Services”. Firewall, Web Services Gateway and EJB Services. 3. Liliana Cabral , John Domingue, Enrico Motta, Terry Payne and 5. CONCLUSIONS Farshad Hakimpour , “Approaches to Semantic Web Services: An Overview and Comparisons”. A complete solution for delivering Semantic Web Services is on the way. Although the 4. Rohit Kumar Shukla , “SOA and the vision for SWS has been set for solving Web Services Framework – The particular issues, only now is the area as a Designing Concept ”. whole taking shape. 5. The state of the art of SWS shows that technologies will shape towards accepted 6. Ivana Trickovic, “Process Definition enabling standards for Web Services and the Capabilities and Web Services”, 27 Dec Semantic Web. Semantic Web Services are 2005. far from mature, while they represent different development approaches 7. Jorge Cardoso and Amit Sheth, converging to the same objective, they “Introduction to Semantic Web Services provide different reasoning support, which and Web Process Composition ”.