RE: [xsl] Using XPATH axis within a recursive structure to match a descendent node

["Michael Kay" <mike@xxxxxxxxxxxx>]

Thanks: it's a faulty optimization.

Saxon is rewriting 

d-or-self::node()/child::load except
d-or-self::node()/child::gui/descendant::load

as

d-or-self::node() / (child::load except child::gui/descendant::load())

which isn't the same at all.

This leads to some interesting questions about what exactly are the
circumstances under which the set operators (union, intersect, except) are
distributive with respect to "/".

[//A | //B] translates nicely to [/descendant-or-self::node()/(child::A |
child::B)] but you've now got me worried! I suspect that union distributes
correctly into any path expression but intersect and except don't - but I'm
not sure I can prove it. Any set theorists out there who can help?

Michael Kay
http://www.saxonica.com/

 

> -----Original Message-----
> From: Pawson, David [mailto:David.Pawson@xxxxxxxxxxx] 
> Sent: 22 February 2005 10:37
> To: xsl-list@xxxxxxxxxxxxxxxxxxxxxx
> Subject: RE: [xsl] Using XPATH axis within a recursive 
> structure to match a descendent node
> 
> Mike, I can't get this to work using saxon 8.3
> 
> xml
> <gui>
>      <load>                                        
>  ........................*0
>         something
>      </load>
>      <p> blah
>            <b>
>                  blah
>                     <load>                                 
>  ........................*1
>                        else
>                     </load>
>                     <gui><load>                                 
>  ........................*2
>                              <again/>
>                           </load>
>                     </gui>
>            </b>
>      </p>
>  </gui>
> 
> 
> XSL
> 
>  <xsl:template match="gui">
>     <!-- <xsl:apply-templates 
> select=".//load[ancestor::gui[1] is current()]" />  <br /> -->
>     <p> <xsl:apply-templates select=".//load except 
> .//gui//load" />  </p>
>   </xsl:template>
> 
> 
>   <xsl:template match="load" >
>     [<xsl:value-of select="."/>] <br />
>   </xsl:template>
> 
> 
> The commented out version works, 
> but the one shown (gui template) doesn't, and I can't see why 
> it shouldn't?
> 
> 
> Any suggestions why please?
> regards DaveP
> 
> 
> 
> 
> 
>  
> 
>     -----Original Message-----
>     From: Michael Kay [mailto:mike@xxxxxxxxxxxx] 
> 
> 
>     In XPath 2.0,
>     
>     .//load except .//gui//load
>     
>     or 
>     
>     for $this in . return $this//load[ancestor::gui[1] is $this]
>     
>     
>     In XSLT (1.0 or 2.0) you could write
>     
>     .//load[ancestor::gui[1] is current()]
>     
>     
>     Michael Kay
>     http://www.saxonica.com/
>     
>     
>     
>      
>     
>     > -----Original Message-----
>     > From: ben senior [mailto:ben@xxxxxxxxxxxxx]
>     > Sent: 21 February 2005 15:15
>     > To: xsl-list@xxxxxxxxxxxxxxxxxxxxxx
>     > Subject: [xsl] Using XPATH axis within a recursive 
>     structure to match 
>     > a descendent node
>     > 
>     > I'm afraid I couldn't think of a better title!
>     > 
>     > Take a look at the xml below. The goal is to match the 
>     load tags of 0 
>     > and 1, but NOT 2.
>     > I need an expression which matches ALL load tags that are 
>     descendents 
>     > of the current gui tag, but not contained within 
>     descendent gui tags! 
>     > Does that make sense to anybody?
>     > 
>     > i.e. descendant::load will also match 2, which I do not want. 
>     > How might
>     > I approach this? Any ideas?
>     > 
>     > <gui>
>     >     <load>                                        
>     > ........................*0
>     >        something
>     >     </load>
>     >     <p> blah
>     >           <b>
>     >                 blah
>     >                    <load>                                 
>     > ........................*1
>     >                       else
>     >                    </load>
>     >                    <gui>
>     >                          <load>                                 
>     > ........................*2
>     >                             <again
>     >                          </load>
>     >                    </gui>
>     >           </b>
>     >     </p>
>     > </gui>
>     > 
>     > Kindest Regards,
>     > 
>     > Ben
>     
>     
> 
> -- 
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