A Semantic Web Service-Oriented Model for E-Commerce Jing Ni[1], Xinli Zhao[2], Lijun Zhu[3] 1
Beijing Institute of Petrochemical Technology, Beijing 102617, China
[email protected] 2 China Science and Technology Exchange Center, China 3 Institute of Scientific and Technical Information of China, China ABSTRACT
E-commerce on the internet provides a high level of flexibility and openness, but it still has many drawbacks due to the heterogeneity of the exchanged information. Web Services have added a new level of functionality on top of current Web, enabling the use and combination of distributed functional components within and across company boundaries, but they offer only syntactical description that are hardly amenable to automation. Developments in the field of Semantic Web Services (SWS) show the opportunity of adding higher semantic levels to the existing frameworks, to improve their usage and ease scalability. In this paper, we outline a Semantic Web e-commerce in which data sources and services are made available through SWS, described by ontologies, allowing interoperability as well as reasoning to create a comprehensive response adapted to user goals. We present a semantic web service oriented model for e-commerce, aiming to integrate the development of Semantic Web services using the WSMO into ISR-III framework, it can also be applied to e-government. Keywords: ontology, e-commerce, web service, WSMO, IRS-III 2. WEB SERVICE 1. INTRODUCTION Web Services (WS) have the advantages of integrating Semantic Web shows great potentials in the business operations, reducing the time and cost of Web e-commerce. A key word searching in current online application development and maintenance as well as shopping is not only tedious and time-consuming but promoting reuse of code over the World Wide Web. A also often results in large amounts of irrelevant Web Service is an interoperable unit of application logic information. Current Web services offer only an that transcends programming languages, operating inflexible interface with some human oriented metadata systems, network communication protocols, and data that describes what the service does, and which representation dependencies and issues. It is an organization developed it. Web Services are typically infrastructure for developing and deploying distributed intended for applications consumption, in contrast with applications. Web Services are based on the following contemporary Web applications which are meant for industry standards: Simple Object Access Protocol human users. However, the lack of machine readable (SOAP), Web Services Description Language (WSDL), semantics is hampering their usage in complex business and Universal Description, Discovery, and Integration environment. (UDDI). Semantic Web Services (SWS) come along and provide a solution with rich formal descriptions of their capabilities, thus facilitating automated discovery, dynamic binding, and invocation of services within an open environment, which can be utilized by applications or other services without human assistance and immune to highly constrained agreements on interfaces or protocols. According to a semantic specification in ontology, a commercial infrastructure can be featured for a better communication between buyer and seller. The rest of the paper is structured as follows: In section 2, we provide a general overview of web services. In section 3, we provide an overview of the semantic web and in particular of those aspects which allow the specification of semantic description for web services. In section 4, we describe Semantic Web Services and compare the main differences between the OWL-S and WSMO. Finally, we propose an e-commerce model based on semantic web service.
SOAP [1] is an XML based lightweight messaging protocol intended for exchanging structured information between applications in a decentralized, distributed environment. SOAP messages can carry an XML payload defined using XML-S, thus ensuring a consistent interpretation of data items between different services. WSDL [2] is the W3C recommended language for describing the service interface. WSDL is used to describe a Web service: to specify its location and to describe the operations the service provides. WSDL-based document provides enough information about how to interact with the target Web service. As services become available, they may be registered with a UDDI registry [3], which represents a set of protocols, can subsequently be browsed and queried by other users, services and applications. UDDI web service discovery is typically human oriented. UDDI
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service registrations may also include references to WSDL descriptions, which may facilitate limited automation of discovery and invocation.
Ontologies are often developed in a collaborative manner by domain experts. Languages for representing ontologies and related issues are discussed in [7]. 3). Logic enables inference - deducing new knowledge from the explicitly stated knowledge and can be used to uncover implicit ontological knowledge. 4). Agents are software programs with sets of beliefs(knowledge about world)，desires(goals the agent works to achieve or fulfill)，intentions(goals or sub goals agent is currently pursuing),behaviors(actions the agent is able to take)that work autonomously and proactively on behalf of a user. The Semantic Web provides the necessary infrastructure for publishing and resolving ontological descriptions of terms and concepts. In addition, it provides the necessary techniques for reasoning about these concepts, as well as resolving and mapping between ontologies, thus enabling semantic interoperability of Web Services through the identification (and mapping) of semantically similar concepts.
Fig. 1 Web Service usage scenario The common usage scenario for Web services (fig.1) can be defined by three phases; Publish, Find, and Bind; and three entities: the service requester, which invokes services; the service provider which responds to requests; and the registry where services can be published or advertised. A service provider publishes a description of a service it provides to a service registry. When a developer realizes a need for a new service, he finds the desired service either by constructing a query, or browsing the registry. The developer then interprets the meaning of the interface description and binds to the discovered service within the application they are developing. This application is known as the service requester. At this point, the service requester can automatically invoke the discovered service (provided by the service provider) using Web service communication protocols (i.e. SOAP)[4].
4. SEMANTIC WEB SERVICE APPROACHES COMPARISION With the development of the semantic web, Semantic Web services (SWS) became an important role. Semantic web services expand the capabilities of a web service by associating a semantic description of the web service in order to enable automatic search, discovery, selection, composition, and integration across heterogeneous users and domains. There are several approaches to define semantic Web services, the most prominent proposals are OWL-S and WSMO. Both proposals have been submitted to the World Wide Web Consortium for standardization.
However, as no explicit semantic information is normally defined, automated comprehension of the WSDL description is limited to cases where the provider and requester assume pre-agreed ontologies, protocols and shared knowledge about operations.
OWL-S [8] is a Web Services ontology that specifies a conceptual framework for describing semantic web services. OWL-S is also a language that enriches Web Services information from OWL [9] ontologies. It is structured to provide three types of information about a service:
3. THE SEMANTIC WEB The Semantic Web is a vision of a Web which can be interpreted by computer programs. The purpose of Semantic Web is sharing and reusing knowledge. Users will be able to search more accurately of the information and the services they need from the tools provided.
1). A Profile that describes capabilities of Web Services as well as additional features (e.g. inputs, outputs, preconditions and effects) of web services for “what” it does.
Semantic Web focus on metadata, ontologies, logic and inference, and software agents [5, 6].
2). A Process Model describes “how” the service “serves” that provides a description of the activity of the Web Service provider from which the Web Service requester can derive the interaction.
1). Metadata is data about data and its aim is to describe part of the meaning of data. It should be explicitly represented to meet the needs of the machine processing.
3). A Grounding that is a description of how abstract information exchanges in terms of the message formats, protocols and communication ports.
2). An ontology is a conceptualization of an application domain in a human-understandable and machine-readable form, and typically comprises the classes of entities, relations between entities and the axioms which apply to the entities in that domain.
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The Web Service Modeling Ontology (WSMO) [10] is a formal ontology for describing the various aspects of services in order to enable the automation of Web Service discovery, composition, mediation and invocation. Its main components are Ontologies, Goals, Web Services and Mediators.
concepts and relations defined elsewhere, by either extending or simply re-using them as appropriate. 3). Web Service descriptions describe the functional behavior of an actual WS. The description also outlines how Web Services communicate (choreography) and how they are composed (orchestration).
1).Ontologies provide the formally specified terminology of the information used by all other components.
4). Mediators define mappings between components: i.e. connectors between components with mediation facilities for handling heterogeneities. Table1 shows the comparisons between WSMO and OWL-S.
2). Goals represent the objectives that users would like to achieve via the WSs. A goal can import existing
Table 1 WSMO Vs. OWL-S. Comparison Aspect Goal Principles
WSMO
OWL-S
Actual goal, specific application
Without explicit goal, does not focus on
domains
concrete application domains
based on the conceptual work
Vague, development based set of tasks to be
done in WSMF
solved
Discovery
Web Services (capability),goal
Composition
Orchestration + choreography
Process Model
Invocation
Grounding+WSDL/SOAP
Grounding+WSDL/SOAP
Both OWL-S and WSMO map to UDDI API adding semantic annotation, also OWL-S and WSMO share a default WSDL/SOAP Grounding. However, a web service description within WSMO contains an interface definition. An interface includes a definition of orchestration – how a composite web service invokes
Profile
subsidiary web services - and choreography. In contras， OWL-S does not provide an explicit definition of choreography but instead focuses on a process based description of how complex web services invoke atomic web services.
Fig. 2 E-Commerce Portal Architecture
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5. THE PROPOSED E-COMMERCE PORTAL ARCHITECTURE
E-marketplace and semantically described via the IRS-III module of the Middleware layer.
The modules (Fig. 2) are organized in three layers. User Interaction supports the user to identify and collect information for service execution.
6. CONCLUSIONS Web services provide a mechanism to connect applications regardless of the underlying software/hardware platform and their location. Commercial organizations can thus use web services technology to expose elements of their business processes. Semantic Web Services enable the formal specification of services, allowing their automated, goal-driven, location and usage. WSMO provides a framework for the description of Semantic Web Services that enables seamless business integration through formal descriptions, maximal decoupling of components, and strong mediation support. In this work, we propose an e-commerce model and make an attempt to integrate the development of Semantic Web services using the WSMO into ISR-III framework. This model can also be taken into e-government consideration.
The middleware layer is the primary layer. Ontology component includes user ontologies of the user layer, this ontology is composed of user oriented concepts. It allows to further specialize the lowered results on the particular interface which is used. Domain ontologies are specialized for description of parameters of the information. For example, an ontology for Visa and MasterCard related WSs specifies the sub-class and super-class relationships for the relevant entities and properties. In this ontology, Gold Card is defined as a subclass of the MasterCard that is the subclass of Credit Card. The properties of Gold Card include apply name, date, location and capital, etc. Like domain ontologies, a WS ontology describes service hierarchies and a subclass of a service inherits the properties and functionality of its super-class service and extends it with its own attributes. The Service ontology contains the SWS definitions. They correspond to instances of the Goal, Web Service and Mediator classes used in the IRS-III module, following the WSMO definitions.
ACKNOWLEDGEMENT This research was supported by the National Natural Science Foundation of China under Grant 70573103. REFERENCES
IRS-III [11], the Internet Reasoning Service, is a framework and platform for developing semantic web services which utilizes the WSMO ontology, which allows the description, publication and execution of Semantic Web Services, according to the WSMO conceptual model. Based on a distributed architecture communicating via XML/SOAP messages, it provides an execution environment for SWS. Especially, it can automatically transform programming code into a web service, by automatically creating an appropriate wrapper. Hence, it is very easy to make existing standalone software available on the net, as web services.
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A request presented by the user through the portal interface is processed by the Commerce Manager module, which discovers all related events, allowing the user to select the appropriate event. Information is described through the domain ontology, while the Goals are described via the Service Ontology. When the user invokes one of the goals, the Commerce Manager calls the IRS-III module, which retrieves the semantic description of the goal. Then, it creates an instance with specific data items, and identifies and invokes the web services addressing the user needs by means of their semantic description. Finally, the web service is executed and the result is presented to the user.
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