Security model

Hi folks,

I am currently evaluating drupal as a possible solution for a community website. The other main contender atm is Plone (running on Zope). I have a few as-yet-unanswered questions but I'll address them one at a time.

So, first up: The Security Model.

I have seen that drupal has the concept of roles and permissions, which is great. What I am unsure about is whether both the roles and permissions can vary for different parts of the site.

I am imagining a situation where there is a sudo-hierarchical structure to the site's content. Within the structure a user may have different roles or permissions depending on where she is in the site (e.g. he may be a moderator in one area but not others, there may be public and private sections of the site). I would like to be able to assign more than one role to a user, again depending on where they are on the site.

Zope has a very good security model and can handle all of this functionality, but I am not sure if drupal can?

I have also noticed a module called 'groups' which has something to do with grouping users for authorization purposes. Does this go beyond assigning roles to users and if so how?

Hopefully, this is all possible with drupal and I just don't know how yet.

Thanks in advance for your help. :-)