The user form is used for editing from the Identity Manager interface. You assign it by assigning a proxy administrator to the adapter. If the proxy administrator has a User form associated with him, this form is applied to the User view at processing time.
You set a proxy administrator for an adapter through the ProxyAdministrator attribute, which you can set to any Identity Manager administrator. All Active Sync-enabled adapter operations are performed as though the Proxy Administrator was performing them. If no proxy administrator is assigned, the default user form is specified.
Best practice suggests keeping common changes, such as deriving a full name from the first and last name, in the User form. The resource form should contain resource-specific changes, such as disabling the user when their HR status changes. However, you can alternatively place it in an included form after the desired attributes are placed in a common path, such as incoming.