Double Slash Needed?

Belch · January 24th, 2012, 09:27 AM

Hi all, very quick and basic question coming up..

I have been using double slash (//) in XPath definitions on occasion for a while now, but realised today that omitting the double slash has the same effect, i.e. all nodes of the specified name are selected just the same.

Is this down to the transformer engine (saxon) being clever?

My understanding of XPath is being shaken to it's core!!

Thanks,

samjudson · January 24th, 2012, 09:36 AM

It depends where you are using the "//" and what you are trying to do.

If you are talking about <xsl:template match="//element"> then you do not need the "//" at all, and this is part of the XSLT spec.

If you are finding something works without the "//" then I suspect you have been using it incorrectly - Saxon is a standards based XSLT processor - it doesn't read minds.

Belch · January 24th, 2012, 09:48 AM

Yes, I was using it as part of the xsl:template match attribute.

Thanks for the info!

mhkay · January 24th, 2012, 10:43 AM

match="//title" means almost the same as match="title", but not quite. The first matches any title element in a document (a tree rooted at a document node), while the second matches any title anywhere. Of course, many stylesheets never process elements that aren't part of a document, and in this case both are equivalent, except for two little details: (a) match="title" is faster, because it doesn't have to check what's at the root of the tree, and (b) match="title" has lower default priority, which only matters if you have several template rules that match the same node.

Belch · January 24th, 2012, 02:06 PM

Thanks Michael, good to know the differences - although we don't process elements outside of a stylesheet as you said.
The lower priority is something to consider though, cheers.