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

2.6 Activity Frameworks for Specification Development 27
Guidelines and Heuristics
An activity framework should be supported by a rich collection of modelling and design
heuristics. Heuristics are informal guidelines representing successful experience
obtained in the past. Heuristics help designers to structure the problem domain, to find
objects, to determine behaviour, to express behaviour in languages, to use supporting
software tools, etcetera.
An activity framework must be supported by a rich collection of
guidelines and heuristics.
Time
Requirements Capture Phase
Behaviour Capture Phase
Refinement / Verification
Refinement / Verification
Refinement / Verification
Realisation Phase
Figure 2.2: A top-down modelling approach
Top-down Modelling
Today most specification methods use a guiding framework in which different modelling
views (see Section 2.3) are created in different modelling phases. For instance, the
formal description techniques LOTOS, Estelle and SDL [Tur93, Pir92, BH93] typically
use a top-down modelling approach. See Figure 2.2. In its purest form this approach
is adopted by the LotoSphere method [Pir92]. It starts by creating a requirements
document. The functional properties of the requirements document are used to derive
a behaviour model. This model completely describes the observable system behaviour
but refrains from internal system structure and internal functions. System structure is
designed in the architecture phase during which the behavioural model is refined in
Architectural Phase
Specification Trajectory