Question regarding how to specify preference for interaction model

WG,

My team does not think we have a clear recommendation for how to specify
the preference for an interaction model (e.g. LDP-RS versus LDPC). We could
use either some clarification / help, or maybe we need to consider clearing
it up better in the spec.

In the code examples within the specification, we can see that the
interaction model is provided by a Link header in responses. For example,
Example 2 of the spec shows the following:

Link: <http://www.w3.org/ns/ldp#BasicContainer>; rel="type",
      <http://www.w3.org/ns/ldp#Resource>; rel="type"


The specification also states:

"Note: The HTTP Link header is the method by which servers assert their
support for the LDP specification on a specific resource in a way that
clients can inspect dynamically at run-time. "

Though the spec refers (links) to more information about the interaction
models, that information it references is in the context of server
responses, not client requests. See below:

5.2.3.4 LDP servers that successfully create a resource from a RDF
representation in the request entity body must honor the client's requested
interaction model(s). If any requested interaction model cannot be honored,
the server must fail the request

- If the request header specifies a LDPR interaction model, then the server
must handle subsequent requests to the newly created resource's URI as if
it is a LDPR. (even if the content contains an rdf:typetriple indicating a
type of LDPC).

- If the request header specifies a LDPC interaction model, then the server
must handle subsequent requests to the newly created resource's URI as if
it is a LDPC.
(Links in the two bullet points above talk about only the Link header in a
server response to a client request; they do not specifically mention any
preference given first by the client)

So, our concern is that it is not clear how a client should state the
preference in a request. Should the client use the Link header or a Prefer
header, for example?

For us, it is unclear.

Thanks in advance for sharing your thoughts,

-- 
Cody Burleson