Re: [xml-dev] xml:base and fragments

[John Cowan <johnwcowan@gmail.com>]

On Wed, May 10, 2017 at 7:23 AM, Andrew S. Townley <ast@atownley.org> wrote:

You’re right.  The specification doesn’t say anything about retrieval other than if the relative and base URI resolve to the same base URI, then dereferencing “should not” result in a new retrieval action.

Note that that "should not" is in lower case: it is not an RFC 2119 requirement.  But even if we interpret it so, there are cases in which a new retrieval is needed to resolve a same-document reference.  One example is when the original document has been transformed in such a way that the fragment identifier is no longer usable, and the original document discarded.

Sameness of resources can only be determined by comparison of the octets and metadata.

Actually, that doesn't work either.  It may be that http://temperature.xyz/podunk and http://temperature.org/squeedunk return the same numerical value because the temperature in Podunk happens right now to be the same as the temperature on Squeedunk, but they are still two different resources.  What is more, http://translation.xyz/fr-en/bavarder and http://translation.xyz/en-fr/cat may *always* return the same string "chat", but they are nevertheless two different resources.

The only way to be sure two resources are truly the same is to find an authoritative owl:sameAs triplet saying so, or an equivalent informal statement.

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