murata at apsdc.ksp.fujixerox.co.jp
Mon Jun 8 17:33:41 BST 1998
John Cowan wrote:
> Since one of the primary purposes of Content-Type: is to instruct
> a receiving program (email client, Web browser, or what have you) on
> the proper application to deploy in order to interpret the
> MIME entity, it seems to me that it would be useful to standardize
> a "type" parameter with application/xml and text/xml. Legal
> values would be "document", "entity" (including both external
> parsed entities and external parameter entities), and "dtd".
Thank you for your comment.
Although the Internet Draft proposes text/xml and application/xml, the
XML WG plans another mechanism for XML packaging (packaging of a
document entity, external entities, styles, a catalog file for
resolving FPI's, and so on.) The Internet Draft is intended to
provide minimum functionalities for successful interchange of XML.
The rest is left to XML packaging. The XML WG might want to introduce
many more parameters of text/xml (e.g, references to DTD's, references
to stylesheets, references to programs, etc.) or might want to
introduce another media type. I do not know yet. (I also have to
admit that XML packaging has not been seriously studied, though.
It would be a service if somebody thoroughly studies this issue and
submits a technical note to W3C.)
Regarding your proposal, an XML document entity can also be an
external parsed entity. XML declartations and text declarations are
designed to allow this duality. Thus, I do not think we should
distinguish "document" and "entity". If we distinguish the two types,
users cannot make an XML document that is also an external parsed
entity. (However, one could argue that the type attribute should
An external parameter entity can also be an external DTD subset.
Thus, "dtd" and "entity" should not be distinguished, as I see it. The only
reasonable thing is to distinguish "dtd" (including parameter
entities) and "entity" (including document entities).
Then, is it necessary to distinguish "dtd" and "entity"? Certainly, a
text/xml-aware MIME recipient can invoke different programs for
"dtd" and "entity". However, it is also possible for an XML-syntax-aware
program to autodetect "dtd" and "entity".
Are there any strong reasons to introduce the "type" parameter in a
hurry? I can be pursuaded, but I am inclined to postpone this issue
to XML packaging. After all, we cannot make a perfect solution at this stage
of the game. In other words, text/xml and application/xml are not
expected to provide enough information for launching XML applications.
They merely provide the charset parameter.
> Typically, "documents" would be passed to an XML browser, whereas
> "entity"s and "dtd"s would be simply stored; alternatively, "dtd"s
> could be passed to a DTD viewer. Passing "entity" or "dtd" MIME
> entities to an XML browser would or could produce an unwanted
> parsing error from the browser.
Fuji Xerox Information Systems
Tel: +81-44-812-7230 Fax: +81-44-812-7231
E-mail: murata at apsdc.ksp.fujixerox.co.jp
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