Add a subelement parameter so that only that element will be considered as root

[janmichaelyu]

Might help when xml documents use the envelope pattern and we want to hide metadata in the view.

[grtjn]

Could be useful.

Note that you can also achieve this by tweaking the url to provide a portion of the XML (or JSON) only, for instance using /v1/docs with a transform param. Alternatively, you could process the XML client-side, and make use of the data instead of the uri attribute on the view-file directive.