W3C home > Mailing lists > Public > public-qt-comments@w3.org > January 2004

[XQuery] value comparisons and empty sequences

From: Daniela Florescu <danielaf@bea.com>
Date: Sun, 18 Jan 2004 08:22:11 -0800
Message-Id: <786BBF50-49D2-11D8-9BA8-0003937198F4@bea.com>
To: "<public-qt-comments@w3.org> <public-qt-comments@w3.org>" <public-qt-comments@w3.org>

The ability to deal with null values (that translate into the XML data 
model
very often as empty sequences as result of path expressions) is a clear
necessity for most real world applications.

Unfortunately in the current specification the value predicates (e.g. 
eq, lt, gt)
raise dynamic errors when one of their arguments is an empty sequence 
and this
poses significant problems while querying data with null values.

In order to solve this problem the value comparisons should simply 
return the empty
sequence when one  of their arguments is an empty sequences.

Please remark that the other form of comparisons (the general 
comparsion "=" and its
family) do deal properly with the empty sequence, but have other 
properties that make
them unsuitable for processing large volumes of data (e.g. they are non 
transitive).

Thanks for your attention, best regards,
Dana Florescu
Received on Sunday, 18 January 2004 11:25:24 UTC

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