Hi Marcus,



This kind of problem can be a fun challenge.



If you don't have a lot of XSLT experience (and sometimes even if you do), 
the hard part of a problem like this is knowing which are the hard bits, 
and which not.



In this case, it's the node selection logic that is the hard part: how do 
you traverse the tree including just the nodes you want? The easy part is 
rendering those nodes as you select them. (Indenting can readily be 
achieved by iterating over ancestors of a node and putting out whitespace 
for each ancestor.)



So how to select the nodes? One clue can be gotten by keeping in mind that 
by default the XSLT processor goes top-down, and in fact since this is how 
you want your rendition to appear, this is the right way to go.



This means translating your logic specifying which nodes you want to 
include to a top-down model. As it happens, this is pretty straightforward:



starting at the document element (not the root node)
A. process all its children
   with each child encountered:
     if it is an ancestor-or-self of your target node
       mark with 'minus', and
       if it's an ancestor, return to A
       if it's the target node, just write the children
     if not
       if it has children, mark with 'plus'
       in any case, write it out

This reduces the logic to a recursive process that is easily enough 
achieved using XSLT's processing model. The only trick is in that test: 
when processing a node, how do you know it's an ancestor of your target 
node (or the target node itself)?



Assume you have bound your target node to a variable:



<xsl:variable name="target" select="//*[@id='somethingorother']"/>



In this case, a current node "." is among the ancestor elements of the 
target, or the target itself, if it passes the following test:



count($target/ancestor-or-self::*) = count(. | $target/ancestor-or-self::*)



(If you want to improve efficiency a mite you can bind the left side to a 
variable, since it's always the same.)



Likewise, the current node "." is the target when



count(. | $target) = 1



(XSLT 1.0 idiom for testing node identity.)



I hope that's enough to get you moving.



Hint: don't traverse up from the target node. Instead, traverse down from 
the document element, testing as you go. The tests will determine whether 
to descend any particular branch of the tree.



Another hint: modes are your friends.



Ask again if I'm being too sketchy here. And good luck,
Wendell

At 04:16 PM 5/4/2004, you wrote:
Hi gurus



I want to generate an "unfolded" tree down to a selected element. So I 
want to render all ancestors to the selected element and all their 
siblings but not the siblings children. Also, the root shouldn't be 
included and I don't want the siblings to the top-level (below the root 
element) ancestor to be included. Another wish is that if the selected 
element is a section element I also want to render it's children (just one 
level though).



Example source XML:



<site>
  <section name="level1_1">
    <section name="level2_1>
      <page name="level3_1"/>
    </section>
    <section name="level2_2"/>
    <page name="level2_3"/>
    <page name="level2_4"/>
    <section name="level2_5">
      <section name="level3_1">
        <page name="level4_1"/>
      </section>
      <page name="level3_2"/>
      <section name="level3_3"> <-- Selected element
        <page name="level4_1"/>
        <page name="level4_2"/>
      </section>
      <page name="level3_4"/>
    </section>
  </section>
  <page name="level1_2"/>
  <section name="level1_3">
    ...
  </section>
</site>

Wanted result (with indents and everything :) :
node name="level1_1"
  node name="level2_1"
  node name="level2_2"
  node name="level2_3"
  node name="level2_4"
  node name="level2_5"
    node name="level3_1"
    node name="level3_2"
    node name="level3_3"
      node name="level4_1" //shouldn't be rendered if page
      node name="level4_2" //shouldn't be rendered if page
    node name="level3_4"

It would also be nice if one could draw something extra to indicate 
whether the node has children or not (like a plus or minus...).



How would you do it? I've made a couple of tries with 
anscestor-or-self::etc but I just tangle myself into hairy loops.



The template/templates that will do this will be called on the selected 
element level.



/Marcus



ps. I'm using MSXML so node-set() is available.




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Wendell Piez                            mailto:wapiez@xxxxxxxxxxxxxxxx
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