Determine when re-write of RDFSource request/response bodies are required, and implement

[birkland]

As API-X provides a proxy endpoint for Fedora, repository resources exposed through API-X have different URIs than their fedora counterparts.  When relative URIs are used in requests and response, there is no issue.  Absolute URIs may need to be rewritten in request and response bodies.  This is akin to mod_proxy_html, except for rdf.

Testing:  

• PATCH, POST, PUT, GET in supported media types (turtle, n-triples, sparql update) where absolute URIs are present
  • Measure latency/throughput impact of doing this

[acoburn]

This W3C document is relevant to this discussion: https://www.w3.org/TR/ct-guidelines/

[ajs6f]

We could use that for fcrepo-transform. Or maybe fcrepo-transform should factor into API-X, actually. Okay, different issue.

[birkland]

@acoburn Yes, though I'm thinking that many (most?) scenarios will resemble what RFC3040 describes as a 'surrogate'. In particular

surrogate
A gateway co-located with an origin server, or at a different
point in the network, delegated the authority to operate on behalf
of, and typically working in close co-operation with, one or more
origin servers.
...
Where close co-operation between origin servers and surrogates
exists, this enables modifications of some protocol requirements,
including the Cache-Control directives in [1]. Such modifications
have yet to be fully specified.

We should also look at contemporary implementations of API gateways to see what best practices are in this regard.