xsl query or transformation language

Henry S. Thompson ht at cogsci.ed.ac.uk
Tue Sep 1 22:00:17 BST 1998

Thanks to Paul G. for correcting my sloppy terminology in referring to
construction rules by the wrong name, my mistake.

And Paul G. and Paul P. are both right that my (a) is better described
as asking of a set of construction rules which one should be used for
a given node, a process in which pattern matching plays a part, but
not the only part.

As for walking the tree, we're ALL right (all right!) on this one.
The 90% case for construction rules in simple stylesheets is for them
to contain templates with xsl:process-children in their midst.  If ALL
construction rules in a stylesheet are like that, then the nodes in
the source tree will indeed yield results which are assembled as if by
pre-order.  But note the next line of the draft:

 "Implementations are free to process the source document in any way
   that produces the same result as if it were processed using this
   processing model."

It's important to remember this:  there is no guarantee of sequential
processing even in the simple case.  Because construction rules are
independent of one-another, it doesn't matter what order bits of the
result tree are constructed in.

However there is one case in which a preorder sequencing is implied, in
which case things look pretty much like querying:

 <xsl:process select='.//target'/>

will process ALL the descendants of the current element whose element
type is 'target' in preorder [this isn't said explicitly in the draft,
but should be:  it is implied in the description of xsl:process]

  Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh
     2 Buccleuch Place, Edinburgh EH8 9LW, SCOTLAND -- (44) 131 650-4440
	    Fax: (44) 131 650-4587, e-mail: ht at cogsci.ed.ac.uk
		     URL: http://www.ltg.ed.ac.uk/~ht/

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