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Re: Media types

From: Mark Baker <distobj@acm.org>
Date: Thu, 10 Jan 2002 13:03:43 -0500 (EST)
Message-Id: <200201101803.NAA26887@markbaker.ca>
To: david.orchard@bea.com (David Orchard)
Cc: www-tag@w3.org, ietf-xml-mime@imc.org
Hi Dave,

> Mark,
> 
> The same concerns I raised in xmlp apply here.  The slippery slope of
> manifests appears.  What about other namespaces and vocabularies?  For
> example, SOAP with my foo vocabulary using xml schema data types would be:
>  application/xml; xmlns="soapns" xmlns="foons" xmlns="datatypesns"
> 
> or perhaps
>  application/xml; xmlns="soapns foons datatypens"
> 
> This would have to duplicata all the xmlns decls in the document.
> 
> Does this make sense?

I understood the slippery slope argument around the "+xml" convention
because the syntax didn't (and couldn't) preclude other "+" things.
But "xmlns" would be restricted to a single URI value identifying
the root namespace.

Note that I'm not really sold on this myself, it just looks pretty. 8-)
An issue with it is that every tool I'm familiar with that enables an
app to be bound to a media type, doesn't permit me to bind different
apps to different parameter values of the same type.  So for example;

  application/xml; xmlns="http://www.w3.org/1999/xhtml"

and

  application/xml; xmlns="http://www.w3.org/2001/12/soap-envelope"

would only be allowed to be dispatched to a generic XML processor
anyhow, who would then be tasked with further dispatch based on the
namespace.  So the parameter doesn't add a lot of value in that case
beyond what would be possible with just "application/xml", except as
a quicker lookup mechanism, which itself comes at the cost of the
complexity of duplicating that information and handling additional
error cases.

I think the need for it (or not) would come mostly from the email
community, which I unfortunately don't have nearly enough knowledge
about.

> The way I see it, media types are broken for multiple namespace'd xml
> documents, especially documents that are targetted to be frameworks like
> soap.  The "+" syntax for media-types simply doesn't scale to these kinds of
> documents.  I don't know how, but we have to find someway of either
> expressing a manifest, or the name of a profile that is a reference to a
> manifest.  At least with the use of xmlns we have some notion of versions as
> well, given the namespace name would be used.

I agree that media types aren't suitable for multi-namespaced documents.
That's why I'm all for making the transition from media types to
namespaces with either vanilla "application/xml", or adorned with the
root namespace.

MB
-- 
Mark Baker, Chief Science Officer, Planetfred, Inc.
Ottawa, Ontario, CANADA.      mbaker@planetfred.com
http://www.markbaker.ca   http://www.planetfred.com
Received on Thursday, 10 January 2002 13:02:57 GMT

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