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- From: Tim Bray <tbray@textuality.com>
- To: David Brownell <david-b@pacbell.net>
- Date: Mon, 28 Jun 1999 16:35:44 -0700
At 04:27 PM 6/28/99 -0700, David Brownell wrote:
>> Distinguish between <!DOCTYPE > and validation. I do *not* agree
>> that parsing DTD syntax takes up 2/3 of a parser.
>
>I did distinguish between them.
...
>Savings may not be 2/3 ... but I'd be _really_ surprised if they were
>less than 1/2. The best way to know is to implement ... :-)
I did.
>But they can become a LOT
>smaller if they don't need to handle even that, and are relieved of
>the responsibilities to handle the syntax and state in a DOCTYPE.
I disagree. We went through this quite a bit in the XML Syntax Working
Group. It is absolutely *not* the case that DTD parsing is demonstrably
very expensive. There was a conventional wisdom floating about that
a parser for a DTD-free dialect of XML could deliver the same performance
and functionality in immensely less space. Empirical analysis fails
to support this contention. Analysis of existing parsers shows immense
amounts of work going into things like reading Unicode efficiently, doing
well-formedness checks on entity nesting, and tracking locations to
support good error messages - I repeat that there is a resounding lack
of evidence to show that parsing DTD syntax is particularly taxing for
any competent programmer. Even parameter entities aren't hard to
implement - they are hard to *describe*, just not hard to implement. -Tim
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