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Re: In lieu of multiple attlists: LINK?



At 22:37 24/2/97 +0100, Steve Pepper wrote:

>The LINK-based syntax that I am proposing is intended to tell an XML
>processor something useful about an existing document without having to
>edit either the document or the DTD. It's just a way to let (say) the TEI
>DTD say: "Hello, I'm the TEI DTD. You don't know me, but I have an xref
>element type which I'd like you to treat as if it were xml-link."

This can only be possible if the element concerned already has all the
information required by an XML link processor in the appropriate form. The
chances that an existing element will have user updatable scheme, locator,
caption and behaviour attributes already, with those names, is extremely
slim. (Hence my comments yesterday on the need to allow for the mapping of
attribute names.)

>Communicating this information can be accomplished without invalidating
>the document with respect to SGML, using the syntax I propose.

Yes, but what elements can they be used on? They cannot be used on the HTML
A because this does not have any of the attributes listed above. It cannot
be used on TEI links, because they do not have some of them. 

(Steve: If LINK could do the job I would be the first to support it - I am
one of the few who have been showing how it can be used effectively for the
last decade.)

>You are talking about a scenario in which a user may want to specify
>different attribute values on different instances of an element type--
>which obviously requires editing the document. Trouble is, as soon as you
>do that--and specify a value for an attribute which is "declared" using
>a magic PI--you no longer have an SGML compatible document.

It is a fact that no 8879:1986 compliant tool will be able to process
documents meeting ANY of the proposals made so far; PI, multiple processing
or LINK processing. They will all baulk the minute one of the attributes
defined by XML has to be added to an instance if it has not been defined as
part of the element's first ATTLIST.

>In short: The magic PI solution (<?xml attlist ... ?>) doesn't give you any
>extra mileage. It's just yet more new syntax for something that already
>exists.

What it buys you, if you start it with <?XML, is that it is a clear
statement that you can only process this document if you have a processor
that understands the XML notation - any other SGML tool will report an error
for it.
----
Martin Bryan, The SGML Centre, Churchdown, Glos. GL3 2PU, UK 
Phone/Fax: +44 1452 714029   WWW home page: http://www.sgml.u-net.com/