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   URI schemes (was Re: [xml-dev] URIs harmful)

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Maybe the problem with URIs is the idea of the "scheme" [1].  Take the
following URI below:


This is a URI that conforms to the "http" scheme.  At the same time, this is
a URI that identifies a specific resource.  Unfortunately, all I want to do
is identify the resource with the URI.  I do not want it to be dereferenced
via http.  So, the obvious thing to do is use a different scheme:


However, this has changed my URI.  Also, the new URI must (should?) now
conform to whatever the "idea" scheme defines for that URI namespace subset.
Of course, you could have a scheme who's definition was "this does not
dereference.  it is just a unique URI string."  But then you have the
problem that Tim Bray mentioned:

> How about for things that you don't have any representations for right
> now but plan to in the near future?  How about things that you don't
> have any way of representing right now, but you might someday?

Later, I may want to change my URI back to the first one above.  Of course,
I would really have two URIs at that point (the "http" and the "idea" one).
I could depricate the "newscheme" URI, but we all know how easily that

In the end, what I really want is something like this:


This becomes my Scheme-Independent Universal Resource Identifier (SI-URI),
totally independent of the scheme.  Now, if I should choose to give
"http://seairth.com/AbstractResource";, one would know to apply the http
scheme to it (and presumably dereference it via http).  Or, if I gave
"ftp://seairth.com/AbstractResource";, one would know to apply the ftp scheme
instead.  I could even give "idea://seairth.com/AbstractResource", in which
case one would apply whatever semantics go with the "idea" scheme.  But,
when I give "//seairth.com/AbstractResource", one would be able to say "this
is a SI-URI.  I can reference this resource globally without applying the
semantics of a given scheme to it."  In all cases, the SI-URI does not
change.  It always identifies the same resource.  I can provide access to
the resource by as many or as few schemes as I want without ever changing
the global identifier.

Seairth Jacobs

[1] http://www.ietf.org/rfc/rfc2396.txt


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