RE: Open systems / Freedom ( was RE: The Web as an Application)

This confuses me greatly.
If an application knows the document is xml (say via a media type derived from application/xml) then the next step I would take as a consumer of the data would be to look
at the namespace of the root element.   That tells me more about the data then anything else.
This is *in band* information not *out of band* information.

Since the media type and the XML content itself is provided in the same HTTP response I dont understand the concept that
the media type is the only reliable semantics.

I have never once had to use nor seen any value in using a media type more specific then application/xml or text/xml


Could you expound on this ?  Maybe I just dont "get it".

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From: Rushforth, Peter [mailto:Peter.Rushforth@NRCan-RNCan.gc.ca]
Sent: Tuesday, September 24, 2013 2:47 PM
To: mca; David Carlisle
Cc: public-xmlhypermedia@w3.org
Subject: RE: Open systems / Freedom ( was RE: The Web as an Application)

In a RESTful system, the (only?) reliable message semantics metadata across servers and clients is the media type.

If you stray outside the media type definition, you are relying on out-of-band semantics.  That might work where you
control the client and the server, but it doesn't scale: application/xml may be a purchase order on my system, but may be a
personal health record in a hospital system.  The only thing those two messages may have in common is
that they have angle brackets.

So anything that implies only what the XML specification implies is not communicating very much to
potential consumers: the least common denominator, as it were.  The suggestion is to add links to that.  It's the web, after all.

Here's another alternative:

Since the definition of xml is separate from the registration of the application/xml media type (from Liam's earlier message),
 what about adding links to the registration only? You don't have to change the definition of xml then, just its definition on the web.

Regards,
Peter




________________________________
From: mca [mailto:mca@amundsen.com]
Sent: September 24, 2013 13:26
To: David Carlisle
Cc: public-xmlhypermedia@w3.org
Subject: Re: Open systems / Freedom ( was RE: The Web as an Application)
registered mime types are important to the web.
working parsers for registered mimetypes are even more important.

the advantage that the XML family has is that it is relativity easy to design and ship your own custom parser (XSLT) with each and every snowflake message design you care to invent.

as long as you only want to speak in XML, all is fine. start using plain text-based formats, JSON-based messages, videos, and other binary messages and suddenly shipping your parser with the message gets a lot harder.

this is all old news.


mca
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On Tue, Sep 24, 2013 at 1:13 PM, David Carlisle <davidc@nag.co.uk<mailto:davidc@nag.co.uk>> wrote:
On 24/09/2013 17:42, Rushforth, Peter wrote:
What's astonishing is how many XML vocabularies rely only on
application/xml on the web.

Why is that surprising at all?

If you have a a vocabulary served as application/xml it can in many
cases just automatically do the right thing, especially if coupled with
an in-document processing instruction such as xml-stylesheet.

If you invent a new xml vocabuary and give it a new mime type, there are
typically few advantages and a massive disadvantage that the default
behaviour for every application is to drop it on the floor as an unknown
mimetype.

We (finally in MathML3, after 15 years of MathML) got round to
registering a mime type for MathML, because some people would find it
useful, but it is of very limited use on the web (most convincing use
case for it is labelling clipboard formats on some operating systems)

David

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