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RE: Treatment of NULL values

From: Babich, Alan <ABabich@filenet.com>
Date: Mon, 16 Dec 2002 12:31:58 -0800
Message-ID: <FBEB6CC95F05FC49A9446D797F7ADE570B6A0F@hq-ex2kpo1.filenet.fn.com>
To: "Julian Reschke" <julian.reschke@gmx.de>, <www-webdav-dasl@w3.org>

Yes. In a "where" condition, if either or both operands of a relational
operator is Undefined (for example, if we allowed arithmetic expressions
as operands to relational operators, division by zero would be
Undefined, and that would contaminate the entire arithmetic expression
to a result of Udefined) or null, the truth value is UNKNOWN.

In "order by", null values and missing strings collate as per the
description in section 5.5.3 you have reproduced below.

So, the description of the "where" condition must make the truth value
clear, and the description of how nulls sort currently in 5.5.3 must be
moved to 5.6 somewhere (the description of "order by").

That has always been the intent.

Alan

-----Original Message-----
From: Julian Reschke [mailto:julian.reschke@gmx.de] 
Sent: Saturday, December 14, 2002 8:15 AM
To: www-webdav-dasl@w3.org
Subject: Treatment of NULL values



Hi.

Section 5.5.3 [1] currently says:

"NULL values are "less than" all other values in comparisons.

Empty strings (zero length strings) are not NULL values. An empty string
is "less than" a string with length greater than zero."

This seems to imply that the value of the expression

	
<lt><prop><some-undefined-property/></prop><literal></literal></lt>

is TRUE. However, I think it should be UNKNOWN.

Shouldn't the statement be rewritten to only refer to the case of
*sorting* results?

Julian


[1]
<http://greenbytes.de/tech/webdav/draft-reschke-webdav-search-latest.htm
l#nu
ll-values>

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Received on Monday, 16 December 2002 15:32:30 GMT

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