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

5.7 Views 131
Behaviour
Behaviour
Unified
Model
Unified
Model
Unified
Model
Architecture
Architecture
Figure 5.7: Growing Specification
from complete (in the upper model in Figure 5.7), the model may already have its final
number of graphical hierarchical abstraction levels. Objects are filled in at various levels
at different times. A model grows by adding objects and clusters by integration of
aspects from various views, simultaneously.
5.7.3 Sorts of Refinement
We distinguish various sorts of refinement. The levels of abstraction are based on the
hierarchy of clusters. We define adding objects, clusters, channels or messages, and
their behaviour on one specific level of abstraction as horizontal refinement. The vertical
decomposition of a cluster into clusters and objects is defined as decomposition refinement.
In our modelling approach composition will be just as important as decomposition. Adding
clusters that group objects (and clusters) is also a form of ’vertical’ refinement. It adds
detail to the model in an upwards directed way. To distinguish between forms of vertical
refinement we define the latter form as composition refinement. Complexity is handled
by separation of views. Refinement will therefore be done from various points of view.
Figure 5.8 visualises this idea. Analysis, done from a safety point of view, adds details
to the specification. It may be that some of these details cannot be formalised. They