Difference between "Groups" and "Roles"?

hi all
i'm trying to write some APIs for "Role Management". now i'm confused about terms "groups" and "roles".
1. are they same?
2. are they different?
3. if they are different then what are the specific notions that differ them?
4. what are the examples that falls into "groups" or "roles" clearly?
i hope you got my question here.
to my view,
"groups" usually refelects physical grouping in a company or something while "roles" reflects logical grouping made for ACLs for general resources you know...
e.g.
- in a company we can have one group for each project which reflects members of the project.
- now per project we would have "roles" for people. some might be developers, one (or more) managers, testers etc...
do i make any sense?
please provide ur views on this. i found myself befuddled if you know what i mean..
regards
maulin

I agree with your description of "roles", but groups is a bit less concrete.
We have apps that have "groups" such as DBAs or Admins, that are cross project and then there is some indication which member of that group is primary for a specific project.

hi Cindy,
yes. DBAs and Admin can be groups.
i observe that groups like DBA represents a notion that doesn't have much to do with ACLs or "management" aspects. on the other hands "roles" often reflects "business structure" i believe.
e.g.
- all managers are able to access their subordinate's details pertaining to the employment. technically this might be
1. going to the company site,
2. login as their ID and
3. then access the tables storing employees' information.
- all DBAs are able to update databases in the domain. Now, it is not of relavence if the loggin DBA is "also a manager" because the interface that DBA will get won't have the functionality to view employees' data (though they can query tables assuming appropriate rights

)...
others, please express your views to help me...
regards
maulin