A method of designing communication service specifications using message sequence charts

A new specification design method for describing communication services is developed. This method describes service specifications in sequence charts and provides a user‐friendly man‐machine interface and specification conversion function. Applying this method to actual specification design showed that: (1) services such as call waiting or teleconference, normally impossible to represent with sequence charts, can now be described; and (2) the amount of specification description (the number of elements in sequence characters plus data required for specification conversion) for services frequently repeating the same signal elements is less than 30 percent of the number of steps in the corresponding service software. For services in which signal elements are not greatly repeated, this amount is still less than 40 percent of the number of steps if 20 percent of the signals can be shared between services.