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

368 SHE Framework
Object Class Models are extended with new classes that emerge from the extension
of the Message Flow Diagrams.
Extended Instance Structure Diagrams are created. Behaviour-Preserving Transformations
can be used to improve structure and map processes to various implementation
resources that are visualised as clusters.
The Unified Model is extended, refined and transformed according to the needs of
all other extended diagrams.
If decisions for a technology can be made well considered, but also early, this is a
big advantage for the efficiency of the modelling. We offer the opportunity to specify
these decisions in the essential phase. However, the separation between essence and
implementation must always be kept in mind. It will be clear that there is such a
wide variety of possible systems and possible technologies that a lot of decisions can
be made only after the Essential Specification is finished. Furthermore the extension of
the model with new objects with corresponding behaviour can cause iterations in the
design because some newly added functionality can form an unacceptable load on the
specified resources.
Because of the wide variety of possibilities it is hard to give generic rules for the development
of an extended model. A designer that learned to use our method in the
essential phase will be able to create an extended model using his design knowledge
and skills. This second model gives the opportunity to explore a specification in depth,
including implementation modelling. An extended model is in general very specific for
different products or systems. Therefore we only illustrate the sort of activities we have
in mind for extended modelling by mentioning examples of various aspects.
11.5.2 Implementation Technologies
During the extended modelling phase the models are extended with directives about
implementations in the form of boundaries and annotations in diagrams in the form of
comments. In this subsection we give an impression of the sort of information we want
to annotate in the models.
On the system level, decisions can be made for one or more:
available hardware platforms;
hardware modules to be developed;
operating systems;
networks based on one or more protocols;
application software layers;
user interfaces;