48 - use document URIs as Named Graphs

[joshsh]

Currently, the Named Graph in which LinkedDataSail stores the data
retrieved by dereferencing a URI is a secondary URI which is inferred
according to a couple of simple rules.  However, this URI should really be
the URI of the document that:
a) was retrieved with a 200 status code after LDS issued a GET request for
it, or
b) was retrieved after a second GET request, after the client was
redirected via a 303 status code

The difficulty is that we need to make the first GET request before we know
for sure what the document URI is.  This means we can't just let the HTTP
client handle 3xx redirection on its own.  Also, there _is_ no document URI
when the first GET request results in an error.  We therefore need to
distinguish two kinds of cached URIs (which will generally correspond to
information and non-information resources).

Original link: http://code.google.com/p/ripple/issues/detail?id=48