Subject: Re: [xsl] is there really a need for location steps of ".."? From: David Carlisle <davidc@xxxxxxxxx> Date: Fri, 14 Mar 2003 10:02:08 GMT |
The chances are that your XSLT system includes rewrite rules that transform these kinds of things from one style to the other, depending on which is the best for the implementation so in practive it may make no difference whatsoever, however if the predicate is expensive to evaluate and you assume wandering around the tree is less so, and you assume the system does no rewrites or optimisations then //part[--complicated-test--involving .]/ancestor::* is on the face of it more efficient than //*[--complicated-test---involving descendant::part] as in the former the complicated test will be done just once for each part element, but in the latter it will be executed on each part element as many times as that element has ancestors. Also of course if the predicate involves last() or position() then you will get different answers, not just different efficiency. David ________________________________________________________________________ This e-mail has been scanned for all viruses by Star Internet. The service is powered by MessageLabs. For more information on a proactive anti-virus service working around the clock, around the globe, visit: http://www.star.net.uk ________________________________________________________________________ XSL-List info and archive: http://www.mulberrytech.com/xsl/xsl-list
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