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Re: XML-*

From: Tim Bray <tbray@textuality.com>
Date: Fri, 06 Dec 2002 10:26:12 -0800
Message-ID: <3DF0EBC4.4080908@textuality.com>
To: noah_mendelsohn@us.ibm.com
Cc: Norman Walsh <Norman.Walsh@Sun.COM>, www-tag@w3.org

noah_mendelsohn@us.ibm.com wrote:
>>>It seems to me that supporting the possibility of 
>>>managing entities should have little impact on 
>>>performance for documents that don't have
>>>any.
> 
> Not true, in my experience.  Depending on one's implementation strategies, 
> the very fact that things can move, expand, and in the case of external 
> entities be in different encodings all can potentially complicate an 
> implementation.  It's not unusual for such factors to lead to an 
> assumption that data will be copied, something which may be hard to avoid 
> in the no-entity special case.

Hmm, my intuition is that if you
(a) removed the possibility of recursion from entities, and
(b) forbid any form of external entity

that would drive the implementation cost down to where it would vanish 
in the static of more expensive stuff like Unicode character handling 
and attribute-value munging.  You're going to have to have code there 
anyhow to do &amp; and &lt; and &#xbabe; anyhow, so it's really hard for 
me to believe that the extra cost would be noticeable.  But I'm old and 
grizzled enough to distrust intuition on this kind of thing, so I 
wouldn't be too surprised to be proved wrong.

Speaking on the (shaky) basis of intuition, it seems like a profile of 
XML with brutally-restricted internal entities (in an internal subset 
only) might hit a real sweet spot, simultaneously solving MathML's 
problems and usable in high-performance protocols a la SOAP.  Worth 
thinking about anyhow. -Tim
Received on Friday, 6 December 2002 13:26:13 GMT

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