How to use group to contain entities?

[<eg_ymc@stu.ust.hk>]

Dear all,

I am doing my final year project, developing an organization model with each person playing multiple roles. Therefore , I would like to use "group" to represent multiple roles, like Managers, Clerks.

However, I come across serveral problems. 
  
1. what are the differences between 
A. "objectclass: groupOfUniqueNames" 
    "uniquemember: cn=Manon Goo, ou=People, o=MG, c=DE"

B. "objectclass: groupofNames" 
    "member: cn=fred blogs,dc=example,dc=com"    ?


2. Can a group contain a member under itself ? For example, Officers is a subtree of Mangers.
       "dn: ou=Managers,dc=example,dc=com" 
       "objectclass: groupofNames" 
       "member: ou=Officers,ou=Managers,dc=example,dc=com"?

3. During  the searching the group, will each member of group automatically be searched? What I mean is the server will automatically search all entities inside the group?

Could anyone help to answer the questions? They are very important to my project.
Thank you for your help.

Yours,
Simon