"At present, the only way a Silva-generated web page on arana could know the identity of the viewer is if it is getting this authentication information from the browser's current session (i.e. the viewer has logged into the DL using their network username and password (via LDAP) and have then opened up a second tab and accessed the web page from there). Is this correct?"
No, I don't think so: the servers are different, running on different urls, and so cannot look in eachother's sessions. The only way the Silva-generated webpage can know the identity of the viewer is if the viewer is logged into *Silva*.
"At present, the only way a Silva-generated web page on arana could know the identity of the viewer is if it is getting this authentication information from the browser's current session (i.e. the viewer has logged into the DL using their network username and password (via LDAP) and have then opened up a second tab and accessed the web page from there). Is this correct?"
No, I don't think so: the servers are different, running on different urls, and so cannot look in eachother's sessions. The only way the Silva-generated webpage can know the identity of the viewer is if the viewer is logged into *Silva*.