code: @Override
  	public boolean addPermission(Permission permission)
  	{
  		if(permissions.contains(permission))
  			return false;
  		
  		return this.permissions.add(permission);
  	}
docs: /* (non-Javadoc)
  @see nyla.solutions.core.security.data.AccessControl#addPermission(nyla.solutions.core.security.data.Permission)