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

5.8 Boundaries 135
x
x Object A y z
Object C
a b
c
Cluster
Object B
Abstraction
Cluster used as
abstraction boundary
that hides an
aggregate.
x
AGGR
Figure 5.9: Abstraction Boundary hiding an Aggregate
in e.g. a specific ASIC technology of a module are examples of design decisions that can
be visualised in Object Instance Models. Implementation boundaries are represented as
clusters or process objects, Graphical representations must be labelled with the abbreviation
IMPL, followed by the name of the implementation technology decided upon,
or a reference to it. The class definition can be extended with a comment following the
class name definition, in the form:
’Cluster type: technology¡ Implementation
’
A precise description of the prescribed implementation technology is filled in for
. Figure 5.11 shows an implementation boundary that prescribes that
technology¡
the cluster is implemented with an ’intel 80960’ microcontroller. This means that the
behaviour of the cluster is implemented as software on this general purpose microcontroller.
Notice that various implementations of instances of one class may require that the class
is refined into separate classes for different implementations.
5.8.2.4 Concurrency Boundary
A concurrency boundary is an enclosure that prescribes an internal sequential behaviour.
This means that collaborating processes inside the boundary are constrained to perform
their joined behaviour sequentially. Only one process can be actively processing.
Essential modelling will start usually by defining as much concurrency as possible.
After all, possible concurrency is not a prescription to implement it as such. Discovering
concurrency possibilities in a model that is constructed from a sequential point of view is
z