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Re: "charClassSub" in restricted character set derivation

From: Taki Kamiya <tkamiya@us.fujitsu.com>
Date: Tue, 7 Oct 2008 18:30:30 -0700
To: <public-exi-comments@w3.org>
Message-ID: <2BB02BBAEAC34F649D2F63B54561EE6A@catarojp>

Hi,

Thank you for reviewing the specification and providing us a valuable
feedback.

We excluded those regular expressions that contain either wildcard (".") or
negative character groups, since those expressions tend to result in
large set of characters. Even those rare cases that are not the case
often have better alternative ways to specify the same effect, such as
[^&#x30;-&#x10FFFF;] can be expressed otherwise simply as [&#x00;-&#x02F;].

On the other hand, character class subtraction is retained because,
unlike wildcard or negative character groups, the operation always
results in a number of characters smaller than that of the 1st operand.
We also found that character class subtraction does not add much
computational burden if it is properly implemented.

Please also note that it is our expectation that schema authors can
provide some help by being aware of the general cost of each operation
and specifying patterns in ways more friendly to EXI processing.

Thanks!

-taki
Received on Wednesday, 8 October 2008 01:31:15 UTC

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