Web Services are used to support application-to-application communication and to address interoperability issues for systems integration project

Web Services are used to support application-to-application communication and to address interoperability issues for systems integration project. A large part of the work on SOA is dedicated to technology. In fact technologies and standards have a crucial role in the success of SOA framework for composite web services 1. By overcoming interoperability limitations, web services allow the integration of existing software systems by exploiting the pervasive infrastructure provided by legacy systems 2.
One way to understand web services is to understand web services standards. Core web services standards including SOAP (Simple Object Access Protocol), WSDL (Web Services Descriptive Language), UDDI (Universal Description, Discovery and Integration) etc., the basic idea of web services is the use of SOAP to invoke software method in remote systems. The web services can be considered as a set of callable interfaces to software programs/components regardless of their implementation. They can be raised distantly via SOAP messaging. Therefore, these programs can provide amenities to other requests using Internet Protocols.
A web services developer usually uses a software tool to generate the WSDL file from the source code of a program in which some public methods marked as web services operations to be accessed by web services consumers. A web service consumer needs to generate a web services proxy(client) to handle the encoding and messaging of an actual web services call. A web services generation software tool that uses a WSDL file as input can generate the web services proxy. The web services client proxy will handle the serialization and de-serialization between internal data types and SOAP data representation.
The UDDI is a registery standards for web services providers to publish their web services. It may be used by a web services consumer to search by web services providers. The role of UDDI tells the relationships with services consumers and providers in the context of SOA.