[xsl] Element selection based on different overlapping descendant subsets

Subject: [xsl] Element selection based on different overlapping descendant subsets
From: "Trevor Nicholls" <trevor@xxxxxxxxxxxxxxxxxx>
Date: Thu, 2 Feb 2006 00:44:57 +1300

I am transforming some poorly designed XML files into documents which
conform to a relatively simple schema. One of the decisions I need to make
involves an element called <TABLE>. There are literally thousands of tables
in my input and literally hundreds of different element types which may be
descendants of tables (these are nothing like HTML tables!) However certain
specific table types are discernable based on the family of elements they
contain, i.e. I can define a set M of element names and if every descendant
of a particular <TABLE> is in this set then it is an M-TABLE, I can define
another set N to identify any N-TABLE, and so on. Individual elements may
appear in more than one set, individual tables may not.

What I am struggling with is how to define this condition in an Xpath. I
know how to identify any <TABLE> that contains a <Cell> descendant, but
<Cell> elements may be in more than one table type - it depends on what
other descendants I can find. Similarly I can identify any <TABLE> that does
NOT contain a <Side> descendant, but again there are multiple table types
that lack a <Side>.

A very simple case can be coded in the following XSL fragment to illustrate
what I mean:

<xsl:template match="TABLE">
<xsl:variable name="descs" select="count(descendant::*)" />
<xsl:variable name="tabx" select="count(descendant::ROW | descendant::CELL |
descendant::A | descendant::CODE | descendant::TYPING)" />
	<xsl:when test="$descs=$tabx"><xsl:call-template name="tableX"
	<xsl:otherwise><xsl:call-template name="tableOther"

This works - and would be quite acceptable if I was choosing between two
types of table and only had half a dozen element names to compare - but it
doesn't scale very well!

My question: is there a "manageably" concise expression that will let me
test whether each and every descendant element of the context element is a
member of a particular set of element names? And similarly (in case this is
more appropriate for certain types) is there an analogous expression that
will let me test whether none of the descendant elements of the context
element may be found in a particular set?

Sorry, I've been struggling with this for several hours and can't find the
sort of thing I'm after in the FAQ either.

Thanks for any help

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