Community Roles
 
 
Roles are the formal parameters of the community type, and are filled subject to:
- the object filling the role having a type which is a subtype of the role type;
 - any cardinality constraints being satisfied;
 - any specific population rules being satisfied
- distinct proposer/authoriser;
 - sharing requirements.
 
 
Community behaviour may allow changes in role binding by substitution or change of cardinality.