FW: Node equality vs. value identity

 

 

Paul Cotton, Microsoft Canada
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-----Original Message-----
From: Don Chamberlin [mailto:chamberl@almaden.ibm.com] 
Sent: Monday, April 15, 2002 6:00 PM
To: howardk@fatdog.com
Cc: Paul Cotton; mff@research.att.com
Subject: Node equality vs. value identity

 


Hi Howard, 
Thanks for the nice example.  I've used it in the next edition of the
XQuery language specification. By this note, I'm also calling it to the
attention of the editors of the Formal Semantics document, in case they
can use it also.
Cheers,
--Don Chamberlin


-----Original Message-----
From: Howard Katz [mailto:howardk@fatdog.com] 
Sent: Tuesday, April 09, 2002 4:21 PM
To: www-xml-query-comments@w3.org
Subject: node equality vs. value identity

I was just looking through the new FS document and noted the short
example
snippet under "2.2.2: Node identity," demonstrating the difference
between
node equality and value equality. For what it's worth, the following two
queries provide an even more succinct demonstration of this distinction:

                <a/> = <a/>                                  => true

                <a/> == <a/>                 => false

I find the second query to be particularly interesting, since at first
glance its results appear quite non-intuitive if you haven't previously
encountered element constructors. It provides, of course, a very
striking
and salutary demonstration of the fact that each application of an
element
constructor generates a new and unique node.

Best,
Howard