Consider an example of an user, A, using the services of a TravelAgent
object, B. Let object B provide services related to travel
reservations and travel arrangments. It might in turn need to make use of the services
of AirlinesServices provided by an object, C. A obtains the reference of B and invokes the makeReservation
method on B. Object
B might specify, attached with its object reference, a set of security
requirements. Let the security requirements specify that Delegation is
required. In SDM, our system will analyse this security requirement attached to an intermediate
object (in this case, object B) and whether A
is willing to delegate (known from A's security specification attached
to its object reference). Mapping this example to the delegation protocol described in Figure
, the underlying system generates a delegation certificate
and passes it on to
B.
Let the travel agent B contact the airline object, C, to make an airline reservation by invoking the purchaseTicket method. At this point, B provides its certificates (preferred travel agent certificate, certified travel agent, etc) along with the delegation certificate issued by A. B acts as a delegate, acting on behalf of A, and makes a request to C. For this request B combines its own privileges (of being a preferred travel agent, authorizzation to make reservations, etc) along with the privileges of the intiator A (as the service might make use of A's credit card, or a travel coupon issued explicitly to A). Thus B makes use of CascadedDelegation facility provided by SDM while invoking the purchaseTicket method on the object C.