Hi Christian,

I should have read the spec more fully. So clearly I will need to create a custom grouping key as the atomization process (fn:data) basically passes over attribute values:

let $val :=
<affiliation>
<organization>Institut für Organische Chemie der Universität Heidelberg</organization>
<country iso-code="DEU"/>
</affiliation>

return data($val)

=> results in "Institut für Organische Chemie der Universität Heidelberg" as a grouping key.

Thanks for pointing me in the right direction.

C.

-----Original Message-----
From: Christian Grün [mailto:christian.gruen@gmail.com]
Sent: 09 January 2016 18:49
To: Hondros, Constantine (ELS-AMS)
Cc: basex-talk@mailman.uni-konstanz.de
Subject: Re: [basex-talk] group-by behaviour for clustering XML fragments

Hi Constantine,

> Incidentally, BaseX is simply unbelievably fast at executing this – a
> million fragments clustered and written out to another DB in 16
> seconds on a laptop. My congratulations on an amazing product.

Thanks!

> If I use the entire XML fragment as a grouping key, something like this:
> [...]
> … then will the grouping be equivalent to the functionality of the
> deep-equal function?

A grouping keys is the atomized value of a grouping variable [1,2]. If this value is prone to be ambiguous, you can create an arbitrary other value, e.g. as follows:

group by $val := string-join($a/*, '; ')

Cheers,
Christian

[1] http://docs.basex.org/wiki/XQuery_3.0#group_by
[2] http://www.w3.org/TR/xquery-30/#id-group-by

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