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Re: Should information be encoded into identifiers?

• From: Liam R E Quin <liam@w3.org>
• To: rjelliffe@allette.com.au
• Date: Sat, 06 Mar 2010 23:03:00 -0500

On Sun, 2010-03-07 at 14:44 +1100, rjelliffe@allette.com.au wrote:
[...]
> Consider the case where you want to validate that your XHTML 5 documents
> only have no <video> links to MPEG files, because you don't want to
> participate in a power grab of the WWW by US corporations, and your only
> tool to do this is XSLT. Or a Schematron based on XSLT. (Or, indeed, XSD.)

I know it's just an example, but... :)

The only reliable way to do this is not to inspect the URIs but to use
HTTP HEAD and check the MIME media type of whatever you get back.  Of
course, a server could randomly send a different format each time...
unless you own the server to which the URI refers, all bets are off.
This decoupling (as you know, Rick, but many people reading this might
not, which is why I need to say it), this decoupling is fundamental to
Web architecture.  It's also why XML NOTATION was broken as designed.

Currently, this isn't something you can do in XSLT - there's another
thread about exactly that, of course.

Best,

Liam

-- 
Liam Quin - XML Activity Lead, W3C, http://www.w3.org/People/Quin/
Pictures from old books: http://fromoldbooks.org/
Ankh: irc.sorcery.net irc.gnome.org www.advogato.org

• Follow-Ups:
  • Re: Should information be encoded into identifiers?
    • From: rjelliffe@allette.com.au

• References:
  • RE: Should information be encoded into identifiers?
    • From: "Michael Sokolov" <sokolov@ifactory.com>
  • Re: Should information be encoded into identifiers?
    • From: "Christopher R. Maden" <crism@maden.org>
  • Re: Should information be encoded into identifiers?
    • From: rjelliffe@allette.com.au