> > There is an arbitrary number of sequences, sometimes 
> containing items 
> > with the same name:
> > 
> > (k, o, p, c, f)
> > (d, e, f, g)
> > (k, f, z, o)
> > (a, b, c, d)
> > 
> > I want to create a master sequence which contains every item once, 
> > preserving the original order.
> 
> Doesn't xsl:for-each-group over combined sequence solves the problem?

No, it puts groups in order of first appearance, which would put f before d.

Regards,

Michael Kay
http://www.saxonica.com/
http://twitter.com/michaelhkay