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xxxML on top of, embedded in XML

From: David Megginson <ak117@freenet.carleton.ca>
Date: Thu, 30 Apr 1998 14:04:03 -0400
Message-Id: <199804301804.OAA00508@unready.microstar.com>
To: www-dom@w3.org
Richard Cohn writes:

 > 1. Suggestions for specification of a DOM for XML applications such
 > as PGML and MathML. Does the working group expect that XML
 > applications use the generic XML DOM specification or a
 > specialization? My perhaps naive take is that the HTML DOM
 > specification is one example of a specialization in that classes
 > are defined that correspond to particular HTML elements and that
 > these classes provide direct access to most element attributes. My
 > current thinking is to leave the Document object as is, but to
 > subclass Element.  All document-wide but PGML-specific info would
 > be tied to the root element.  This is different from the HTML DOM
 > but seems more general and more interoperable.

The DOM provides an object model for generic documents, and such a
model will be very useful for general formatting, editing, archiving,
and searching processes.

However, it seems to me that PGML implies a very different object
model of hierarchical and linked graphic components, and that it would
be inefficient to build a DOM tree first, only to tear it down and
build a vector-graphics object tree in its place.  Why not design a
PGML object model, and build it directly from an event-based API?  The
difference in overhead for a large (say, 1GB) vector graphics file
will be enormous.

 > 2. Supposing the answer to 1 is that a specialized DOM for PGML and
 > other XML applications is expected, has thought been given to how
 > to integrate multiple DOMs? It seems that MathML or PGML embedded
 > in a more general XML document would be considered a
 > DocumentFragment. This all should 'just work', but as the XML
 > people have found with namespaces, there can be lots of interesting
 > details to work out.

As I mentioned above, the DOM is a solution to a specific problem.
Every XML document implies some kind of object model -- sometimes (as
in the case of a technical manual, a poem, or a novel), the DOM will
be a very good match; other times (as in the cases of serialised
components, vector graphics, or an XSL stylesheet), the DOM will be
too far from the optimal object model.

All the best,


David Megginson                 ak117@freenet.carleton.ca
Microstar Software Ltd.         dmeggins@microstar.com
Received on Thursday, 30 April 1998 14:04:14 UTC

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