Re: IDL?

David Megginson (ak117@freenet.carleton.ca)
Sun, 28 Dec 1997 20:31:43 -0500


Matthew Gertner writes:

> Please correct me if I am wrong, but couldn't the phases in the
> "life" of an XML document be summed as follows:
> Text -> Events -> Grove There is no point that I can see in going
> from a tree-based view
> back to an event stream. The event stream is merely an evolution on
> the path from text to a grove. Furthermoe, nothing I have seen in
> the SAX proposal looks anything remotely like a simplified DOM. We
> are talking about two complete different concepts here.

An event-based call-back interface would be useful for automatic
traversal of a DOM tree (rather than iterating through an
enumeration), but the callbacks should then take DOM nodes as
arguments.

Personally, I believe that an event-based interface is almost always
more difficult to use and understand than a tree-based interface -- it
requires the user to manage stacks and allocate objects herself. On
the other hand, for advanced programmers, and event-based interface
has important advantages:

- it allows linear processing of very large documents with very little
memory

- it can save the waste of building two separate trees, when the user
needs to build a different kind of tree from the XML document

For me, then, the advantage of a common interface was not to help
naive coders, but to provide a standardised low-level access to XML
documents; to strain an analogy, SAX-J would be the IP to the DOM's
TCP.

All the best,

David

-- 
David Megginson                 ak117@freenet.carleton.ca
Microstar Software Ltd.         dmeggins@microstar.com
      http://home.sprynet.com/sprynet/dmeggins/

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