Designing the Service Contract - Oracle SOA Suite 11g R1 Developer's Guide - page 348

Clicking on the Browse… button will launch a window from where you can select
the corresponding XML Schema that the WSDL is referring to, as shown in the
following screenshot:
By default, the window will list all the schemas defined to the Service Bus, though you
can restrict the list by defining the search criteria. In the case of our "orderFulfillment"
service, just select the schema Order_v1_0.xsd , and click on Submit .
This will take you back to the Edit References screen and click Save . This will take
you back to the View/Edit WSDL screen, which should display the confirmation The
References for the WSDL "orderFulillment" were successfully updated .
Your WSDL can now be used to define a proxy service in the normal way.
If you import a schema into the Service Bus, which references
other schemas, then you will need to go through a similar
process to define all its dependencies.
Strategies for managing change
One of the key design principles behind SOA is that systems should be designed
and built to accommodate future changes in response to ever-changing
business requirements.
So far, we have looked at how to design and build the initial system, so that when
change does occur, it can be isolated through the use of service contracts to particular
parts of the overall system.
While allowing us to restrict the impact of change, it doesn't completely mitigate all
the complexities, especially when you consider that the consumer and provider of a
service may be in completely separate organizations.