At least one role must be defined in a collaboration.
Each role definition has the following form.
![\begin{smalltab}
\= {\bf role} $<$role name$\gt$\space \\ \\ gt \{ \= \\ \\ gt \...
...ns$\gt$\space \} ] \\ \\ gt \\ gt $<$rules$\gt$\space \\ \\ gt \} \end{smalltab}](img20.gif)
A conference bus declaration is optional.
We can define roles which do not interact with other local components.
The conference bus is used for communication between the cocavm
and the collaboration tools for each role.
So channel names declared in a role are local to that role.
Predicate isa/2 can be used to test if a given participant
(some self) is currently in some role.