National Research Inst. for Mathematical Sciences, Pretoria, Report No. CSIR-TWISK-506, 1987.
Also in: Int. J. Man-Machine Studies, Vol. 28, pages 437-455. 1988.
Abstract: The requirements of man-machine dialogue specification techniques are examined. Petri Nets are identified as possible candidates for a modelling technique for dialogues on the basis of their applicability to concurrent, asynchonous systems. Labelled Petri Nets are extended to Nested Petri Nets, allowing transitions to invoke sub-Nets. It is shown that this extension allows Nested Petri Nets to generate at least the set of context-free languages.