few plt related questions

[Wojciech Sobczuk <sopel@freebsd.hbz.pl>]

hey,

i'm wondering whether it's possible to do the following in plt scheme:
- protect my scheme environment from the execution of some code.  what i'd like   to do is execute a user-provided scheme program from my server and be sure
  that it doesn't mess with my internal variables - my first idea was to use
  namespaces and a custodian.
  i'd also like to, for example, restrict the program's access to a specific
  directory - so that it can't modify files which don't reside in the given
  directory.
- send various scheme objects over the net (preferrably encrypted - with 
  OpenSSL or a similiar lib) - are there tools for this already or do i have
  to write some up?
- access relational databases (i've seen a postgresql interface for scsh which
  seems easy to port..) - any other such utils?
- any object oriented DBMS'es in scheme around?  would be great if one could
  nicely make scheme objects persistent without all that SQL fuss.  or is that
  another tool that needs writing?

thanks for any responses!

greetings,
Wojtek