Specification of Reactive Hardware/Software Systems - Electronic ...

16 On Specification of Reactive Hardware/Software Systems
Architectural
Views
Timing
Views
Requirement
Views
Unified
System Model
Conceptual
Views
Behavioural
Views
Figure 2.1: Views of a Unified System Model
and disposal, prescribed technologies, prescribed implementation details, safety
requirements, quality requirements, etcetera.
Behavioural views model the behaviour of the system. They focus on the communications
between the system and its environment and the temporal order
in which communication take place. They further describe the data
that is exchanged and the transformations that are carried out on this data.
All current object-oriented methods offer behavioural views. Most of them
[R 91, CY91a, CY91b, J 92, Boo91, SM88] typically support dynamic models (statetransition
models) and/or functional models (data-flow models). This also holds
for the Statemate method [H
90] and for structured analysis and design methods
[WM85, HP88]. Formal description techniques based on LOTOS, SDL and Estelle
[Tur93, BH93] as well as the ROOM method [SGW94] do not really offer separate
explicit behavioural views. These methods rather focus on the creation of a unified
system model. The LotoSphere method [Pir92] however, offers an additional
behaviour view described in the action-based temporal logic CTL [CES86]. In LO-
TOS, SDL and Estelle behaviour is described in terms of communicating processes
(Estelle calls them modules). Very complex behaviour is the major characteristic
of reactive hardware/software systems. To express complex behaviour adequate
modelling concepts are required. These concepts are studied in Section 2.5 and in
chapter 6.