Hi,
It's an interesting fine point that a simple join of this kind is not
possible in unassisted XPath 1.0, where there is no way to bind $this.
The current() function is a way of providing the functionality, but
it's not in XPath 1.0 either as Mike Kay points out.
Of course, the XSLT 1.0 solution, beyond going straight to current(),
is to define a key....
Cheers, Wendell
On Wed, Jun 17, 2015 at 2:00 PM, Liam R. E. Quin liam(_at_)w3(_dot_)org
<xsl-list-service(_at_)lists(_dot_)mulberrytech(_dot_)com> wrote:
On Wed, 2015-06-17 at 14:28 +0000, Malecki, Piotr
piotr(_dot_)malecki(_at_)thyssenkrupp(_dot_)com wrote:
Hello,
The question corresponds basically to XPATH 1.0 (not 2.0 , not XSL).
I have an XML like this (snippet only):
<library>
<catalog>
<book id="_1" name="Book1"/>
<book id="_2" name="Book2"/>
<book id="_3" name="Book3"/>
</catalog>
<customer>
<borrowed bookId="_1"/>
<borrowed bookId="_2"/>
</customer>
</library>
In an application (Windows WPF / XAML), my execution context is e.g.
the element "borrowed" (e.g. <borrowed bookId="_1"/>).
I have to find the name of the book which is referenced as bookId.
So my XPATH expression is like this:
"//book[@id=self::*/@bookId]/@name"
Read as: give all books whose id equals to the bookId of the current
node.
Although you can read it that way, remember that predicates change the
current node for evaluating the predicate. So the current node for
//book[anything]
will be each book element in the document.
A way to do this in pure XPath is to use two steps. First make an
Xpath variable binding, e.g. to "this", as the borrowed book, and then
use
//book[@id = $this]/@name
Note also that some XPath engines can't return standalone attribute
names, so you have to return the list of matching elements and iterate
over them in the host language.
Liam
The Query is executed for the "borrowed" node (execution context).
Unfortunately the expression doesn't return the result expected
(rather an empty set).
What is wrong in my understanding here?
Thank you
regards
Piotr
Mit freundlichen Grüßen / Kind regards
Dipl.-Ing. Piotr Malecki
Systemingenieur / Systems Engineer
Waffen und Führung Systemintegration
Weapon, Command & Control System Integration
Operating Unit Surface Vessels
ThyssenKrupp Marine Systems GmbH
Hermann-Blohm-Strasse 3 - 20457 Hamburg- Germany
P:O.Box 10 07 20 - 20005 Hamburg - Germany
Phone: +49 (0) 431 / 700 2446
Fax: +49 (0) 431 / 700 1600 2446
Mailto:piotr(_dot_)malecki(_at_)thyssenkrupp(_dot_)com
ThyssenKrupp Marine Systems GmbH
Chairman of the Supervisory Board: Dr. Hans Christoph Atzpodien
Executive Board: Andreas Burmester (Chairman), Dieter Rottsieper,
Dr. Walter Klausmann, Torsten Könker
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