[xsl] parameters in XSLT 2.0

[Bruce D'Arcus <bdarcus@xxxxxxxxx>]

I've got a few questions about using parameters in XSLT 2.0:

First, am I right that if I use an "as" attribute of element() or 
node() I am passing a reference to the original element or node, and 
thus that this is an efficient operation?

Related, am I correct that these below are equivalent from a processing 
standpoint?

<xsl:variable name="foo" select="bar" as="element()"/>

<xsl:variable name="foo" as="element()">
  <xsl:sequence select="bar"/>
</xsl:variable>

Finally, in general, under what conditions should one use tunnel 
parameters?  I do a lot of parameter passing in my stylesheets, though 
the content of those parameters is typically fixed.

Bruce