WHAT IS A WEB SERVICE
Definition: An application that is straightforward, independent and can perform functions from the simple ones to the complicated that is from the individual request to the large business request is termed as a Web Service. The web services model uses Web Services Description Language (WSDL), Universal Description, Discovery and Integration specification (UDDI), Simple Object Access Protocol (SOAP) and extensible Markup Language (XML). With the help of WSDL the software systems of one business can be used for the purpose of other business. To invoke the services over the World Wide Web the protocols used are SOAP and the mechanism chosen is XML.
For an example suppose there are two companies such as sister concerns and they know everything about each other’s business. In a condition like this both the companies can link their SOAP interfaces, and this can be done if and only if the security of each other is not breached. In an organization where the web services have unidentified users the languages such as WSDL are used. (Australian Government 2005)
A simpler definition: A web service is an application component accessible over open protocols.
History/Background: Dating back to 1960’s many large software companies including Microsoft were facing difficulties in software-development projects. This led to the origin of the structured programming so that the programs which were created were simple, intelligible, and easily changeable and this happened in 1970’s. It was only in 1980’s and 1990’s that the use of structured programming became popular and the software development process became easy and interesting. But still the developers needed some way to exchange data/information in varied locations and under unsuited platform/language. This problem was referred to as the problem of interoperability. In June 2000 Microsoft gave a term which was widely accepted that is ‘Web Services’. Web services advanced from the knowledge of earlier technologies which were designed to meet the purpose like RPC, DCOM, CORBA and JAVA RMI.
Web services solved the problem of Interoperability by using open standards so that the components of the software are easy to understand and workable. Web Services also proposed to solve the problem of Firewall traversal and Complexity (ESIF 2004).
Motivation: As discussed in History, before Web Services Enterprise Application Integration was used. The motivation for the Web Services was the capacity to program the Web. With the use of Extensible Markup Language the developers were able to design the web effectively and easily and the information between the people and the computers was swapped easily. For example: consider an Excel spreadsheet which recapitulates the accounts of the employees of a certain stock company. By using the XML Web Services, the information can be updated and presented to the user (Zebedee 2004)
General purposes of web services:
Easy Usability The main purpose of the Web Services is its easy usability. The programmers can use any language and can work on any platform and hence deploy it.
Interoperability: This is achieved by using XML which allows the developers to write applications in any language and can be exchanged with other Web services applications.
Web Services have limited sources and they can be re-used.
Ever-Present: The use of Internet for Web Services allows these services to be accessed from everywhere. These services conform to the present security procedures such as firewalls (Zebedee 2004).