Client preferences

The Editor's Draft available on 2014-07-18 states that LDP Paging clients
must include the header

Prefer: return=representation

as a way to advertise their ability to support LDP Paging.


I worry about hijacking RFC 7240 in this way.  There is nothing in RFC 7240
which says that the response should contain a partial representation. So
how can it be regarded as a signal of support for LDP paging?  How would
the server distinguish an LDP Paging client from any other client that is
using "return=representation" in accordance with RFC 7240 simpliciter?


Moreover, there will surely be circumstances where the client does not know
in advance that the URI that it is dereferencing happens to be a paged
resource.
In that case, it won't know that it needs to add the Prefer header.

What's supposed to happen if this header is absent?

Regards,
Greg McFall