The data model for some Web services is extensible. You can enter XML definitions of data model extensions in a custom profile (for more information, see Section 14.2.1, Modifying Service and Profile Details for Employee, Custom, and Personal Profiles). Data model extensions hook into the existing Web service data model at predefined locations.
All schema model extensions reside inside of a schema model extension group. The group exists to bind model data items together under a single localized group name and description. Schema model extension groups can reside inside of a schema model extension root or inside of a schema model extension. There can only be one group per root or extension. Each root is hooked into the existing Web service data model. Multiple roots can be hooked into the same location in the existing Web service data model. This conceptual model applies to the structure of the XML that is required to define data model extensions.
The high-level view of the data model extension XML is as follows:
<SchemaExtensions> <Root> <Group> <Extension> <Group> <Extension>...</Extension> <Extension>...</Extension> ... </Group> </Extension> <Extension> <ValueSet> <Value/> <Value/> </ValueSet> </Extension> ... </Group> <Root> <Root>...</Root> ... </SchemaExtensions>