Web Services (What is WSDL and UDDI)-Part(2)

In our earlier session, we have already seen what is a web service is and How do a service provider and service consumer talk to each other using web services. So let us see where do WDDL and UDDI fit into the architecture of web services.

Web Services Description Language (WSDL).

So If you are a service consumer and if you want to use a web service. You need to know all the services about the Web Service. What the Web Service is? What are the various components? What are the various functionalities? What are the parameters? The return types and How exactly consume the web service. So you need to know everything about the web service. The structure of the web service and the entire description. To enable this every service provider publishes his description of web service and this is a kind of a web service where all the attributes and functionalities of the web service are described. And this an XML based interface and this is called Web Services Description Language (WSDL).

So web services description language is an XML based interface for web services that describe all the attributes and functionality of web service. And why is it XML based? Because it is machine-readable and we can use some tools and some programming language to pass this document and generate the request and response structure. In case you can find an example online.

https://svn.apache.org/repos/asf/airavata/sandbox/xbaya-web/test/Calculator.wsdl

Here you can see this format is XML and it has all the functionality of the web services. It might be a little difficult to read and get everything through this document. Therefore we have tools we can pass this XML and generate all the stuff from this document for the web service.

Now finally we can say WSDL is an interface for the web service and the service provider creates this interface for his web service and service consumer to get this WSDL and use all the web services.

Universal Description Discovery and Integration(UDDI)

Now there are two ways the Service consumer can get the WSDL document. One way is if the service consumer and the service provider all know each other then the service provider can handover directly the WSDL document or the WSDL URL to the client and then the client can use this web service. Now the other case is the service consumer and the service provider does not know each other how can service consumer get the WSDL document?

To enable this all the web services provides publishes their description of their web services to a WSDL to an online registry or a directory that can be searched by any consumer and can get the whole of their WSDL. And this online registry or directory is called UDDI.

So UDDI stands for Universal Description Discovery and Integration(UDDI). And it is an online registry where a service provider can publish his WSDL and consumer can query and get the WSDL. Then once a consumer has the WSDL and they can make use of the web service. This is all about the WSDL and UDDI at a very basic level.

Thank You!