xml-dev - Re: Associating DSSSL style sheets with documents

[Tim Bray <tbray@textuality.com>]

At 05:14 PM 3/14/97 -0600, Len Bullard wrote:
>IOW, what the PIs you suggest do is put metainformation inside 
>an instance.  Why?  What is it they will convey that an XML engine 
>will not already know by reading the specification or could know 
>by reading a DTD?  

Well, a DTD, considered as metadata, is pretty thin.  It doesn't 
contain any semantic information, nor much in the way of strong
data typing.  I can't think of much that is useful for downstream
processing that would naturally live inside a DTD.  The problem of
packaging, of tying the things that you *do* need (stylesheets,
topical metadata, typing rules) to documents is a real one and worth
spending time on.  But there is no reason to believe that a DTD
is a very important part of such a solution.

Secondly, the distinction between data and metadata is, at a deep
level, bogus; totally in the eye of the beholder.  For this reason,
it is always good and never bad to make what the author may
consider metadata available along with what the author
considers data.  Because the author is usually wrong.

>[re PI's:]  I'm wondering why they are suddenly a preferred 
>practice when they were formerly a deprecated practice?  What is 
>worse, a DTD I send once and might be very small, or PIs I send 
>every time?

Reasonable people may disagree.  I have no trouble in saying that
I think that PIs are a useful thing, and a necessary part of real-world
document processing.  Thus, yes (gasp) I disagree with the language
in the SGML standard deprecating PIs, and I see no reason for us
to consider ourselves bound by it.

As for once vs. many, I think that it is in general A Good Thing
for documents on the web to be self-contained whenever possible.
And while I think it is indeed smart to try to avoid retransmitting
fixed ancillary files (metadata, stylesheets, whatever), I don't
think that this class of files includes DTDs that often for the
downstream processing tasks I've seen. - Tim


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