there is no capability for a feature like this.
in Spotfire 10 there is a feature called "Sites" which effectively creates unique libraries per server joined in a cluster, but I don't think it's feasible to create one server per user, and currently I understand there are some issues with clusters containing more than four servers [citation needed]. but the feature is interesting and new so, there you have it.
what I would recommend instead is to get creative with your library permissions (doc is for version 6.5 but these have not changed). in your example:
- /
B+A
for Everyone group (this is required)
- DNA
B+A
or Inherit
for Everyone group (otherwise nobody will be able to see it)
- UserFolder
B+A
or Inherit
- User_xxx do not
Inherit
, B+A+M
for that specific user
the effect will be that all users can navigate up to the User_xxx level, but will only be able to see folders to which they have A
permissions.