Opening Xlinks in a new window

Hello all,

I'm using the DocBook 1.72 stylesheet to create a CHM file from a
DocBook V5 document.
If I use DocBookV4.x, I can use the ulink.target parameters

<xsl:param name="ulink.target" select="'_blank'"></xsl:param>

This would transform DocBookV4 ulinks
<ulink url="http://mypage.com">LINK</ulink>
to
<a href="http://mypage.com"  target="_blank" >LINK</a>

and open the link in a new browser (not the CHM HTML engine in my case)

How can I do the same with DocBook V5 and Xlinks, i.e. set a link to
open in a new browser window?
It seems that the xlink:show attribute has no effect.

Thanks for your help.

Best Regards,
Yannick Deltroo