Java Reference
In-Depth Information
•
A service broker
: Responsible for helping clients determine the location of one or
more
service providers
•
One or more service providers
: Responsible for providing remote computing facili-
ties such as computation and object exchange to clients
•
One or more service requestors
: The clients that use the broker to find the provider
and interact with the provider
■
Note
In the discussion that follows, I use the term
client
to refer to the service requestor.
Figure 13-1.
A schematic representation of a web service
In a classic web service, the requestor first discovers what web services are available
by coordinating with the service broker using the Universal Description, Discovery, and
Integration (UDDI) registry protocol; once the requestor determines what services are
available from a provider, the requestor and provider communicate about the actual
services available using the Web Services Description Language (WSDL). Actual
requestor-provider communications utilize the Simple Object Access Protocol (SOAP).
UDDI, WSDL, and SOAP are all XML applications in that they use XML as the base lan-
guage for representing data. In practice, HTTP carries the requests and responses that
these languages encode, although of course any reliable protocol capable of carrying
object data and metadata about objects would suffice.
