This section describes a list of technologies that related to Web services.
There are several technologies that are related to Web services:
UDDI (Universal Description, Discovery and Integration) - A server acting like a Web service directory.
Web services can be registered and discovered on a UDDI server.
WSDL (Web Services Description Language) - An XML based language to describe a Web service.
SOAP (Simple Object Access Protocol) - An XML based protocol used to define requests and responses for a Web service.
HTTP (Hyper-Text Transport Protocol) - An Internet communication protocol used by the World Wild Web system.
HTTP are used to deliver Web service requests and responses.
XML (eXtensible Markup Language) - A markup language used to organize information in clear text format.
The following diagram is an illustration of how these technologies are used to deliver a Web service from
a provider to a consumer:
Query for a service
Web service <-----------------------------------------> UDDI server
consumer Return provider location |
|
|
Query for the service description v
Web service <-----------------------------------------> WSDL document
consumer Return service description server
|
|
Send service request (SOAP + HTTP) v
Web service <-----------------------------------------> Web Service
consumer Return service response (SOAP + HTTP) provider
As you can see from this diagram, UDDI and WSDL are really optional. If you know the location and
the description of a Web service, you don't need to query the UDDI server and fetch the WSDL document.
All you need to do is to build a request in SOAP format, and sent it via HTTP to the provider.
Since HTTP is a very old protocol, I will not discuss it in this book.
Most of the notes in this book will be on SOAP, because it is the key technology of Web services.
Of course, some of the notes will be on UDDI and WSDL.
