Dynamic Discovery of Web Services using WSDL

Published Online September 2014 in MECS DOI: 10.5815/ijitcs.2014.10.08

Web services are loosely coupled, self- contained software modules that can be accessed programmatically using existing Internet technology, found and assembled dynamically to serve a particular function, solve a specific problem or deliver a particular solution to a customer.

[15]The combination of Service Oriented Architecture and Web services will be used to provide a rapid integration solution that will quickly and easily align Information Technology investments and corporate strategies by focusing on shared data and reusable services rather than proprietary integration products.

In a web services scenario a web application sends a request message to a service at some URI using the SOAP(Simple Object Access Protocol) over communication protocols like HTTP, SMTP or FTP. The service receives the request message, processes it and returns a response message. The URI of the service might be known or might be discovered using UDDI.

Existing Web Service discovery methods classified into two categories. WSDL-based and Ontology- based. In ontology based method annotation have been made to reference to a domain ontology through the standard WSDL extension mechanism. Ontology based methods aims to provide ‘semantically enriched’ version of WSDL files in order to automate complicated tasks such as service composition. But ontologies are static in nature.

Therefore in this paper we have given an approach of web service discovery using WSDL based method. Normally Web services are described by WSDL documents while semantic web services use Web Ontology Languages(OWL-S) as a description language. WSDL based discovery is most popular and supported by both industry and development tools. WSDL based method is further divided into 1)Text based 2)Structure based 3) Semantics based methods.

Text based method is the most straight forward way to conduct Web service discovery. The most widely used text-based method is keyword matching built in the UDDI public registry.

UDDI API also allows developers to specify keywords of particular interest and it then returns a list of web services whose service description contain those keywords. Beyond the literal keyword matching, research in XML schema matching has applied various string comparison algorithms (e.g. prefix, suffix,edit distance) to match different spellings. This method is particularly useful for scientific Web services where many special terms, jargons, and acronyms are widely used in their service descriptions. For example, a bioinformatics Web service might have an operation called ‘DNACombo’, which shall be relevant to a user search ‘DNACombination’. The literal keyword method cannot tell the equivalence between Combo and Combination.

Using UDDI API a link to WSDL will be found and WSDL elements texts are extracted, analyzed, and expanded. But due to pitfalls given in the[2][3][4] we are retrieving WSDL using search engines and will be processing those WSDL files.

This paper demonstrates how it can be achieved by discovering the web services using WSDL based methods which have proper operation of web services according to the user requests during run time. The organization of this paper is, section II gives literature review, section III gives overview of the model, section IV gives dynamic search of web services with WSDL records, section V gives processing of WSDL elements to interpret the functionality, section VI gives generating WSDL from java, section VII gives finding web services using UDDI and section VIII and IX gives results and conclusion.

• II.    Literature Review

In Paper[1] Service mining is used to discover and compose web services which make use of the service usage logs. But our research does not depend on any template information prior to discover because of dynamic discovery.

Chen Wu and Elizabeth Chang [2] indicated that Public UDDI Business Registry - the primary service discovery mechanism over the Internet - has been shut down permanently since January 12, 2006 due to several reasons. This has made the most important public Web service discovery mechanism missing from the Web Services Community.