[Zope] Accessing user id in scripts

Hi all I'm planning a site where users and site structure are held in Zope, but the data items belonging to users are held in an RDBMS, due to their number and relative light weight. I've designed the database so that owned objects have a userid field, and am about to add a mySqlUserFolder for site users, but I'm stuck trying to see how to get a user id from the session so that I can use it my scripts that then call Z SQL methods to do database accesses (insert into things (owner, thing ) values( 'joe123', 'newthing'). I feel like I've run up against a wall in the Zope Book, has anyone done something similar, or can you recommend some further reading? Thanks in advance Will -- Will Stephenson