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Subject: RE: [dita] mime type for DITA?

While a mime type can define a fragment identifier syntax, there is always the question of what tools will recognize and implement that fragment identifier syntax.  Presumably, in the DITA case, it will just be DITA tools which already recognize the syntax.  So defining a mime type specific fragment identifier syntax does allow us to say our href values are true and official URIs, but it doesn't change too much in practice.  (I don't see the argument as either strongly for or against whether we should define a dita mime type.)
Using application/dita+xml to allow tools to recognize dita content sounds like a benefit. Again, though, you have to ask what tools will actually access the mime type and recognize--and do something special--with the dita mime type.  The answer again is just dita tools which already recognize dita content.  So the only benefit might be making it a bit easier for such tools to know they have dita without looking inside the content.
But note that one can get a mime type only from mime headers, and one has mime headers for a file in only rare cases in practice (and half the time when you do have them, they are wrong or incomplete).  The rest of the time, tools guess mime type by looking at the file extension or inspecting the content, and this can and is already done.
So defining a mime type probably has only a minor benefit in practice.
I would counsel against trying to define multiple mime types.  Given the small benefit of mime types in general, if we try to get too complicated here, we'll pretty much guarantee that there will never be two fully interoperable implementations, and I don't see the benefit of multiple mime types.

From: Erik Hennum [mailto:ehennum@us.ibm.com]
Sent: Thursday, 2008 March 27 18:47
To: dita@lists.oasis-open.org
Subject: [dita] mime type for DITA?

Hi, Technical Committee:

Returning to an old question, should the committee take a position with respect to a mime type for DITA?

A DITA mime type would let tools declare and recognize DITA content in HTTP headers, email, and so on without actually inspecting the content. As I understand Paul's note, a mime type would also provide a basis for defining the DITA reference syntax within URI standards:

One might expect DITA to have a mime type similar to application/dita+xml following ordinary practice for XML vocabularies:

DITA is an architecture, however, not a vocabulary. Section A.14 in the relevant RFC suggests that an extensible architecture should prepend qualification levels:

Applied to DITA, that would seem to call for a mime type that separates the declaration of the vocabulary (as defined by the shell for the document type) from the DITA architecture from the XML architecture.

An application that recognizes a document type can process any document that generalizes to a valid instance of the recognized document type. Because of shell pluggability, however, the mime type alone can't reasonably provide a basis for determining the compatibility of a document type accepted by an application with the document type of the supplied document. (The mime type for the document type would have to encode the modules and ancestor modules included by the shell, effectively cramming the value of the domains attribute into an identifier.)

A reasonable compromise might be for the mime type to identify only the base vocabulary. (That compromise also acknowledges the impracticality of registering all DITA shells as mime types.) Applications would have to inspect the domains attribute in the content for more specific evaluation of acceptability. This approach avoids creating a legacy that would have to be accomodated if future work solves the document type compatibility problem some other way.

In summary, this approach would introduce two fundamental mime types for topics and maps:

Because the DITA values file isn't specializable (doesn't provide the architecture attributes), their mime types should identify the XML vocabulary but not the DITA architecture:

Hoping that's useful,

Erik Hennum

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