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Re: Opacity and mailto: in conflict

From: Norman Walsh <Norman.Walsh@Sun.COM>
Date: Mon, 22 Sep 2003 10:53:55 -0400
To: Tim Bray <tbray@textuality.com>
Cc: www-tag@w3.org
Message-ID: <87he34x4ak.fsf@nwalsh.com>

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/ Tim Bray <tbray@textuality.com> was heard to say:
| Norman Walsh wrote:
|
|> In section 2.2, URI Opacity, we say:
|>   Although it is tempting to guess at the nature of a resource by
|>   inspection of a URI that identifies it, this is not licensed by
|>   specifications; this is called URI opacity.
|> Then later on we say
|>   mailto URIs identify mailboxes; ftp URIs identify ftp files and
|>   directories; etc.
|> It seems to me that these two statements are in conflict. Either you
|> aren't allowed to guess the nature of a resource from its URI, or you
|> are: it can't be both ways.
|
| Not in the slightest.  It is perfectly OK for software to look at the
| URI scheme and act on that basis, the semantics of URI schemes are
| well-documented.  The problem is looking into the opaque part, i.e.
| assuming that http://www.tbray.org/ongoing/Biz is a directory, or that
| http://example.com/foo.html yields HTML when dereferenced.  Does the
| spec need to be clearer on what's OK and what's not? -Tim

Yes, if that's what we mean, I think we need to be clearer about what
part of the URI is opaque. What you're saying is that the scheme part
is NOT opaque, but everything else is. Adopting that position begs a
couple of questions:

- - If the scheme specification explicitly identifies other parts of the URI,
  does that make those parts transparent as well? For example, suppose that
  mailto: says that the string that follows it is an email address. Does
  that mean I can infer that any-damn-fool@nwalsh.com is an email address
  if I'm presented with this URI: mailto:any-damn-fool@nwalsh.com ?

- - Does the HTTP spec constrain the range of HTTP URIs to things that are
  documents (or information resources or whatever we're calling bags of bits
  the end of a wire these days)?

                                        Be seeing you,
                                          norm

- -- 
Norman.Walsh@Sun.COM    | Worrying is the most natural and spontaneous
XML Standards Architect | of all human functions. It is time to
Web Tech. and Standards | acknowledge this, perhaps even to learn to do
Sun Microsystems, Inc.  | it better.--Lewis Thomas
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Received on Monday, 22 September 2003 10:55:15 GMT

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