Information Technology Reference
In-Depth Information
dynamically discover and invoke Web services. UDDI was originally
designed as a registry and brokerage system that helped users locate
services needed in a dynamic way. For example, assume that the hotel
industry adopted UDDI standard for hotel room rate checking and
reservation. Hotels could then register their services into a central
UDDI directory. Individual travelers or travel agencies could then
search the UDDI directory to find any hotel's reservation interface.
When an interface is found, users would be able to communicate with
the service directly.
A UDDI business registry consists of three components:
White Pages. They give information about the business providing
the service. Using white pages, users can look for services based
on providers.
Yellow Pages. They provide a classification of the service or
business, based on standard taxonomies.
Green Pages. They describe how to access a Web service,
including the interface, parameters, and address of the service.
WSDL, SOAP, and UDDI were originally designed to be the three
pillars of Web services. However, UDDI does not enjoy as much
popularity as WSDL and SOAP do.
Interface
WSDL [24] (Web Services Description Language) is an XML-based
interface definition specification for describing Web services and how
to access them. WSDL describes a Web service, along with the message
format and protocol details for it.
Figure 1.5 shows a skeleton of aWSDLdocument.
1
Such a document
describes a Web service by using the following major elements:
<
types
>
: Types section defines the data types used by the
service. Types will be referred by the message section.
1
Here we use WSDL 1.1 specification as an example. This is because that, although WSDL
2.0 specification has been released since 2007, we found many public available Web services
are written in WSDL 1.1. For a comparison of WSDL 1.1 and 2.0, please see Reference [28]
W3C. “Web Services Description Language (WSDL) Version 2.0 Part 1: Core Language.”
Retrieved January 7, 2012, from http://www.w3.org/TR/wsdl20/.
