> I'm propably wrong,

I'm afraid so:-)

> The only difference is that my template doesn't compare the attribute values
> as-is, but applies a substring before doing so.

No the string function completely changes the sematics of =.

If you have an XPath test of the form

(node-set a) = (node-set b)

then it is true if _any_ node in set a has a value equal to any node in
set b.

That's what you have here:

@country=preceding-sibling::city/@country

@country and preceding-sibling::city/@country
both select node sets.

If you have

(string a) = (string b)

then this is true if the string a equals to the string b.

that's what you have here:

substring-before(@href,'#')=substring-before(preceding::a/@href,'#')

as substring-before always returns a string.

substring-before requires a string as its first argument and if you give
it a node set (as here) then it takes the string value of the first node
(in document order) of the node set.

@href has at most one node but preceding::a/@href has perhaps many node but
whatever the current node the first node in that collection is the first
href attribute on an a element that occurs in the document.

David

_____________________________________________________________________
This message has been checked for all known viruses by Star Internet
delivered through the MessageLabs Virus Scanning Service. For further
information visit http://www.star.net.uk/stats.asp or alternatively call
Star Internet for details on the Virus Scanning Service.

 XSL-List info and archive:  http://www.mulberrytech.com/xsl/xsl-list