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CHAPTER 9 / DESIGN METHODOLOGY FOR TELECOMMUNICATION SERVICES 95
9.5 CONFLICTS AMONG TELECOMMUNICATION SERVICES
When telecommunication services are described in predicate logic, there are pos-
sibilities for conflict with other telecommunication services. In this section, exam-
ples of conflict and conflict resolution are discussed.
(1) Call waiting service (Figure 9.13): When terminal A calls terminal B
while terminal B and terminal C are talking to each other, the system lets terminal
B know of the arrival of the call. This is call waiting service.
(2) Call forwarding variable service (Figure 9.14): When terminal A calls ter-
minal B while terminal B is busy, the call is forwarded to terminal D, which has
been designated by terminal B as the forwarded terminal.
(3) Conflict resolution (see Figure 9.15 for examples of service descriptions
that come into conflict and the rales by which such conflicts are resolved): When
an event dial(A, B) occurs, system checks states A and B. State A is a dialtone for
both (1) and (2) and state B is idle(B) for both (1) and (2). Initial states (1) and (2)
are the same for the event dial(A, B), so the system cannot choose one rale in a
consistent manner. This requires conflict resolution.
FIGURE 9.14 Example of call forwarding variable.
