On Thu, Mar 13, 2014 at 11:56 AM, David Carlisle <davidc@xxxxxxxxx> wrote:
> On 13/03/2014 11:38, Ihe Onwuka wrote:
>>
>> By all means reply but from an educational perspective point out that
>> your preference for for-each-group,  has no set-theoretic
>> interpretation,
>
>
> It's iterating through representatives of the quotient set if you factor
> by the relation implied by the group-by clause.
>

A union (B difference A). People who speak English will understand that.

>
>> will not work for anybody restricted to XSLT 1.0
>
>
> It's easy to rewrite any such use of for-each-group as xsl-for-each plus
> a filter using a key (look up muenchian grouping for the details)
>

Easy for who?

Where's that quote from Mike Kay that use of xsl:key should be common
knowledge in XSLT development - which obviously suggests that it is
not.

>> and does not port to XPATH or XQuery.
>
>
> For xquery you can use the similar group-by clause so long as you
> are using V3 http://www.w3.org/TR/xquery-30/#id-group-by
>

For the cognoscenti who have access to 3.0 processors,  the same group
of people that almost have nothing to learn from reading any of this.