reading Session objects

[beyaNet Consultancy]

Hi,
I have a session which is created on authentication of a user. As part of the session, the user object is passed back to the sitemap. I was under the impression that I could read the object from the session like ${session.getAttribute("usr").firstName} in my xsl page? I can read the user object into an xsp page by doing:
</xsp:expr>, but how can I read the session object into an xsl page?

many thanks in advance