Re: union and difference

Your definitions for $set1 and $set2:

  <xsl:variable name="set1" select="set1"/> 
  <xsl:variable name="set2" select="set2"/> 

will always result in *disjoint* node-sets. $set1 contains the first
four <set1> nodes while $set2 contains the first four <set2> nodes.
Since a <set1> node is always distinct from a <set2> nodes, these two 
node-sets will never have any nodes in common.
Therefore, when you attempt set intersection with

  select="$set1[count(.|$set2)=count($set2)]"> 

you get an empty node-set and when you attempt set difference with

  select="$set1[count(.|$set2)!=count($set2)]"> 

you get all four nodes in $set1.

The situation is different when you use

  select="$set1[. = $set2]"
  select="$set1[not(. = $set2)]"

Here you are comparing the *text* values of the nodes in node-sets
$set1 and $set2. The first select statement returns the nodes in
$set1 (ie <set1> nodes) which have the same text value as nodes 
in node-set $set2. The second select statement returns the nodes 
in $set1 which do not have the same text value as nodes in node-set 
$set2. You might contrast these two select statements with the 
following:

  select="$set2[. = $set1]"
  select="$set2[not(. = $set1)]"

These statements while having similar set logic, return nodes in 
$set2 (ie <set2> nodes) not nodes in $set1 (ie <set1> nodes).

Finally, I am not sure I agree with another reply with regard
to merging of text nodes. I beleive the following definition of
$set1 will in fact have four distinct nodes:

  <xsl:variable name="set1" select="set1/text()"/>
  <xsl:value-of select="count($set1)"/>

Adjacent text nodes get merged on occassion but perhaps 
some could clarify precisely when this happens as I am not 
100% certain.

Regards,

Dan

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