Wow.. that is easy except that I do not understand your notice
explanation... the difference between your not( ... ) and your !=.
"@cat != 'BLUE'": will be true if the context node has a
'cat' attribute
*and* if it has a 'cat' attribute not equal to 'BLUE'. So
it's the same as
"boolean(@cat) and not(@cat='BLUE')"
"not(@cat='BLUE')": will be true if the context node has no 'cat'
attribute *or* if it has a 'cat' attribute not equal to
'BLUE'. So it's
equal to "not(@cat) or not(@cat='BLUE')"
Let's try to phrase it a different way. An expression such as X=Y in XPath
is shorthand for
some $x in X, $y in Y satisfies $x=$y
in other words, it's true if there's some pair of values from the two sets
that are equal.
Similarly, X!=Y is short for
some $x in X, $y in Y satisfies $x!=$y
which is true if there's some pair that are not equal.
This means that if X is an empty set, then X=3 and X!=3 must both be false.
If you're testing an attribute, @A=3, then @A is a set that's either empty
or contains one node. If there's no A attribute, then @A!=3 is false
(because there's no A that's not equal to 3), but not(@A=3) is true (because
it's not true that there's an A that's equal to 3).
Michael Kay
http://www.saxonica.com/
--~------------------------------------------------------------------
XSL-List info and archive: http://www.mulberrytech.com/xsl/xsl-list
To unsubscribe, go to: http://lists.mulberrytech.com/xsl-list/
or e-mail: <mailto:xsl-list-unsubscribe(_at_)lists(_dot_)mulberrytech(_dot_)com>
--~--