Proposed Framework for Semantic Web Services

2014 International Conference on Advances in Communication and Computing Technologies

Proposed Framework for Semantic Web Services Ms.Mudra Doshi

Ms.G.Anuradha

M.E. Student in Computer Engineering Dept. Faculty of Computer Engineering St. Francis Institute of Technology Mumbai University Mumbai-400103. India. [email protected]

Associate Professor, Department of Computer Engineering St.Francis Institute of Technology, Mumbai University Mumbai- 400103, India [email protected]

Abstract—A Semantic Web is able to describe things in such a way that computers can understand easily. Statements are built using syntax rules, which are the rules for building the language. The Semantic Web is not about links between pages. The Semantic Web describes the relationships and properties between things. There are different ways of converting the existing web pages into semantic web pages. The primitive one uses a reverse engineering approach. A reverse engineering approach is to specify Web Service according to the Web Service Modeling Ontology (WSMO). It describes a model–driven Web Service reverse engineering process, where Web Service Descriptions (WSDL) are transformed to UML models, which are then integrated into composite Web Services and finally the new Web Services Descriptions are generated i.e. OWL. Another approach is Semantic Annotation Web Service Description Language (SAWSDL) interfacefiles by using transformation rules. The proposed architecture is a result of the combinationabove two existing architectures. Keywords—Web Services, Model Driven Approach (MDA), Web Ontology language(OWL), Web Service Description Language (WSDL), Semantic Annotation WSDL (SAWSDL), reverse engineering, Unified Modeling Language (UML), Ontology

I.

encoded in the form of unambiguous, machineunderstandable components. Fig 1 shows the “layer cake” of the Semantic Web [1],which describes the main layers of the Semantic Web design and vision. The bottommost layer is Uniform Resource Identifier(URI) and Unicode, which follows the important features of the existing World Wide Web (WWW). Unicode is a standard of encoding international character sets. The upper next layer for Framework of Semantic Web is Extensible Markup Language (XML). XML lets one write structured Web documents with user-defined vocabulary and is particularly suitable for information interchange across the Web. The XML Name space Schema is used for this purpose. The next layer Resource Development Framework (RDF) is a basic data model, like the Entity-Relationship model i.e. ER Model, for writing simple statements about Web objects (resources). The RDF data model does not rely on XML, but RDF has an XML-based syntax. Therefore, in Fig. 1, it is located on top of the XML layer. RDF Schema provides modeling primitives for organizing Web objects into hierarchical structure. RDF Schema is depends on RDF.

INTRODUCTION

Web pages are primarily designed for human interpretation and use. In addition to providing Web Services, we are seeing increased automation of Web Service inter-operation, primarily in Business to Business (B2B) and e-commerce applications. Generally, such inter-operation is realized through APIs (Application Programming Interfaces) that incorporate hand-coded information-extraction code to locate and extract content from the HTML syntax of a Web page presentation layout. Unfortunately, whenever a Web page changes its presentation layout, the API must be modified in accordance to prevent failure. Instead of relying on computer programs or agents to implement such changes, Web Services are utilized. These web services being Semantic in nature takes care of largescale interoperation and makes services computer interpretable. These Semantic Web Services are

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Fig 1. Framework of Semantic Web [1]

RDF Schema can be viewed as a primitive language for writing ontologies. But there is a need for more powerful ontology languages that expand RDF Schema and allow the representations of more complex relationships between Web objects.

On the Semantic Web, vocabularies define the concepts and relationships used to describe and represent an area of concern. Vocabularies are used to classify the terms that can be used in a particular application, characterize possible relationships, and define possible constraints.

operation’s concept, (c) The data type of each input – output variable is mapped to an object property’s range, (d) Each operation is mapped to a particular web service, and (e) Each restriction is mapped to an axiom.

The Logic layer is used to enhance the ontology language further and to allow the writing of application-specific declarative knowledge. The Proof layer involves the actual deductive process as well as the representation of proofs in Web languages (from lower levels) and proof validation. Finally, the Trust layer will emerge through the use of digital signatures and other kinds of knowledge, based on recommendations by trusted agents or on rating and certification agencies and consumer bodies. Sometimes “Web of Trust” is used to indicate that trust will be organized in the same distributed and chaotic way as the WWW itself. Being located at the top of the pyramid, trust is a high-level and crucial concept: the Web will only achieve its full potential when users have trust in its operations (security) and in the quality of information provided [1]. II.

RELATED WORK

The Semantic Web proposes to help computers to "read" and use the existing Web. The idea is behind Semantic Web is metadata added to Web pages can make the existing World Wide Web machine readable. Semantic Web Services (SWS) enriches Web Service technology by adding formalities, ontology – based descriptions of service functionalities and capabilities at the semantic level. [2]. The aim of semantic web services is to allow discovery, selection, composition and execution of web services. This is achieved through the following steps as given by figure 2. In a nut shell the semantic web transforms the current, syntactic web page into a semantic web page which assists and helps human users to find meaningful datawhile interactacting with the web. Fig 2.hastwo principle stages: (a) A stage of reverse engineering for identification of the useful information, and (b) A stage of engineering for construction of web services according to WSMO.The steps of figure 2 are as follows. Information Extraction phase is an automated process that parses a WSDL file of an existing Web Services to extract the useful information. During this phase, the useful information between the … is identified, i.e. input, output and XML Schema part related to this tag. In Analysis Phase, mapping for each of the extracted components is done. Some rules for mapping are: (a) Each WSDL operation is mapped to a concept, (b) Each input – output variables of each operation are mapped to object properties of the

Fig 2.Generation of Semantic Web Services from Existing Web Services [2]

In Ontology Elaboration Phase, Ontology is created manually using information extracted and analyzed during previous phases. Once ontology is created, it is checked for consistency and at the end exported to OWL file. In Enrichment Phase, semantic annotation to the OWL file is provided by using uploaded domain ontology. Each concept from the OWL file is compared against concepts from the domain ontology. The Translation Phase will translate this OWL file to a Semantic Web. Model Driven Architecture (MDA) proposed by Object Management Group (OMG) is an approach for creating and refining models and generating codes from models. The purpose of MDA is to ensure an architectural separation of concerns between the specification and implementation of software. InMDA approach the WSDL files are reverse engineered into UML models. The generated UML models are then integrated and composed with relevant domain ontologies. The OWL descriptions are generated from the composite UML models [4]. As shown in Fig 3, the first step of this MDA approach is Discover Web Service, which selects the existing candidate Web Services that can be usedin the composite service.

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Fig 3.MDA Approach for Web Service Composition [3] Fig 4. Combined Architecture

Then by ReverseEngineering the necessary Web Services descriptions are imported into UML diagrams. Thisresults in one or more UML models.In Model Composite Web Service step UML tools are used to review and integrate the imported service models to form composite Web Service. Domain ontologies are integrated to this UML models which can be searched from business communities.The models obtained in previous steps are transformed to OWL in Transform composite Web Service step.Finally, the service is ready for publishing in Implement and Publish Composite Web Service [3]. SAWSDL (Semantic Annotations for WSDL) is a W3C recommendation standard. The main advantage of using SAWSDL is that it is extensible and compatible with the WSDL standard. The main objective of MDA is (Model – Driven Architecture) for composition of semantic web services. This will help in the mapping WSDL to SAWSDL and vice versa [5] [6]. III.

PROPOSED WORK

The Semantic Web Service is expressed in OWL or SAWSDL. There are 3 different approaches for developing Semantic Web Services. A. From WSDL to OWL B. From WSDL to UML and then from UML to OWL C. From UML to SAWSDL A.

WSDL to OWL

This is the first approach for building Semantic Web Services from existing Web Services. Here, the existing Web Service is reverse engineered and the WSDL Meta model is obtained. Then this WSDL Meta model is converted directly OWL Meta model using five phases as described in Fig. 2. The mapping of WSDL metamodel to OWL metamodel is shown in Table I [2]. TABLE I.

Semantic Web Services gives meaning to the existing Web Services or to the newly created Web Services. These semantics are given considering the domain of the service. WSDL is the main ancestor for all the Web Service development. Most of the Web Services use WSDL, thus for developing Semantic Web Services, it is necessary to understand the structure of WSDL. This structure can be acquired by reverse engineering process.

WSDL Element Service Definition Port Type Message Part Operation Bindings Input Output Fault XML Schema

Semantic Web Service can be described in many languages like OWL, SAWSDL, RDF, etc. Fig 4.shows the proposed approach for building semantic web services. Here, the existing Web Services are reverse engineered and WSDL Meta model is obtained. This WSDL Meta model forms the base for adding semantics and developing semantic web services.

MAPPING FROM WSDL TO OWL [3]

B.

OWL Construct OWLClass Ontology OWLClass OWLClass OWLClass, Property Operation Operation Constraints Constraints Constraints OWLClass

WSDL to UML and UML to OWL

This is the second approach where the web services are reverse engineered and WSDL

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metamodel is obtained. This Meta model is mapped into UML Meta model. The mapping of WSDL to UML is as shown in Table II [5]. The main advantage of this approach is that it can be used for developing new Semantic Web Services by using UML metamodel of the application rather than studying existing Web Service [3]. TABLE II.

MAPPING FROM WSDL TO UML[3]

WSDL Element Service Port Definition Port Type Message Part Operation Bindings Input Output Fault

UML Component Component Component Port Package Interface Class Attribute, Parameter Operation Dependency Usage Usage Usage

MAPPING FROM UML TO SAWSDL [5]

UML Component Package Interface Class Attribute, Parameter Operation Dependency in param out param in fault out fault

IV.

Once the UML metamodel is obtained, the definition is provided depending upon the domain of the services. This UML metamodel is then mapped onto OWL metamodel [6]. The mapping from UML to OWL is shown is Table III [3].

TABLE III.

TABLE IV.

SAWSDL Element XMLSchemaElement XMLSchemaElement XMLSchemaElement WSDLPart WSDLOperation SAWSDLSchemaMapping WSDLInput WSDLOutput WSDLInfault WSDLOutfault

EXPERIMENTAL RESULT

To map the WSDL to OWL Protégé Tool has been used. The Protégé-OWL editor is an extension of Protégé that supports the Web Ontology Language (OWL) [7]. Protégé is a free, open-source platform that provides a growing user community with a suite of tools to construct domain models and knowledge-based applications with ontologies [8]. Experimental results on BravoAirwhich is an imaginary Web service which provides an online reservation andpurchasing service for airplane tickets. Fig 5 shows a simplified version of BravoAir is as follows.

MAPPING FROM UML TO OWL [3]

UML Component Component Component Port Package Interface Class Attribute, Parameter Operation Dependency Usage Usage Usage

OWL Construct OWLClass OWLClass Ontology OWLClass OWLClass OWLClass, Property Operation SubClass, SubProperty Constraints Constraints Constraints

C. UML to SAWSDL SAWSDL (Semantic Annotation for WSDL) is for Semantic Web Services that WSDL is for Web Services. SAWSDL uses the same framework proposed by WSDL but also provides annotations that means, furnishing the explanatory notes. This furnish is adding the domain knowledge for ontology elaboration. Thus, each element will have some meaning within a domain thus making it semantic Web Services. The mapping of UML to SWASDL is shown in Table IV [4].

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Fig 5. Protégé Tool

build on XML's. Semantic Web has ability to define customized tagging schemes and RDF's flexible approach to representing data. If machines are expected to perform useful reasoning tasks on given documents, the language must go beyond the basic semantics. The need for a Web Ontology Language formulates design goals, requirements and objectives for OWL.Thus, the proposed combined framework provides a template which consolidates the mapping between any two languages irrespective of approach followed. References [1] [2]

[3] Fig 6.WSDL2OWLS Dialogue

Fig. 6 shows the snapshot of conversion from WSDL2OWLS. The output is displayed in the form of a text file. V.

CONCLUSION

[4]

[5]

[6]

Industry is slowly moving towards semantic web services. The Semantic Web is a vision for the future of the Web, in which information gives an explicit meaning to making it easier for machines to automatically process and integrate information available on the Web pages. The Semantic Web will

[7] [8]

Antoniou, Grigoris,“A semantic web primer”, the MIT Press, 2004, ch 1, pp.17-20. Houda El Bouhissi, Mimoun Malki, “Reverse Engineering Existing Web Service Applications”, IEEE Computer, October 2009, pp 279 – 283. Weijun Sun, Shixian Li, Defen Zhang, YuQing Yan, “A Model–driven Reverse Engineering Approach for Semantic Web Services Composition”, IEEE Computer, May 2009, pp 101 – 105. http://netgroup.uniroma2.it/twiki/pub/SWS/UmlResources/re presenting-wsdl-with-uml.pdf, “Mapping WSDL to UML”, 05/10/2013. Fatima-Zahra Belouadha, Hajar Omrana and Ounsa Roudiès“A model-driven approach for composing SAWSDL semantic Web Services”, IJCSI International Journal of Computer Science Issues, Vol. 7, Issue 2, No 1, March 2010. http://www.omgwiki.org/lib/fetch.mapping_uml_to_owl, “Mapping UML to OWL”, 10/10/2013. http://protege.stanford.edu/overview/protege-owl.html, “Protégé Tool”, 09/11/2013. http://protege.stanford.edu/overview/, “Protégé Tool”, 09/11/2013.

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