MIME types and file extensions for XML
ricko at allette.com.au
Mon Jun 8 09:45:42 BST 1998
> From: owner-xml-dev at ic.ac.uk
> The only question I have is that they're
> registering text/xml and application/xml.
> Are we expecting all XML-encoded
> files to transfer under these two MIME types,
> or will more specific MIME types emerge
> for particular types of XML documents?
Anyone can make their own MIME type. The media
types have an extension mechanism. So if I made
"Rick's Markup Language" I could use the media
type "application/x-rml". The "x-" prefix allows
Of course, if Robin Cover made up "Robin's Markup
Language" with the same type name, there is a
This is the old "public identifier" problem.
And the old solution is appropriate: the name should
include some owner name which will promote uniqueness.
If possible, this owner name should be from some
In my case, I am pretty sure there is no one else
in the world with my name. So I can just say
something like "application/x-rick-jelliffe-ml"
and there will be no problems. Robin Cover might
say "appplication/x-sil-org-sgml-ml" and use some
version of his internet domain name, since his
name is less rare and there is slightly more chance
of collission (though still less!).
You can also apply to the IETF and get your own
registration tree. So Microsoft, for example,
could apply for "ms": then they could have
"appplication/ms-rml". (But no-one has done this yet,
so it perhaps involves too much effort to be
a viable alternative.)
(For more on this subject, see chapter 13 "Formal
Public Identifiers" and chapter 14 "Data Content
Notations" in my book. The RFCs for MIME media-type
registrations are useful too.)
The XML & SGML Cookbook, by Rick Jelliffe
Charles F. Goldfarb Series on Open Information Management
656 pages + CD-ROM, Prentice Hall 1998, ISBN 0-13-614223-0
http://www.phptr.com/ > Book Search > "Jelliffe"
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