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

348 SHE Framework
Notice that the Requirements Catalogue and the Response Time Requirements are two
parts of the method that have been worked out rather shallow. Both parts will be subject
of future research.
11.4.4 Modelling of Architecture Structure
Sensors/
Actuators
Feeder
Controller
Sensors/
Actuators
Sensors/
Actuators
Sensors/
Actuators
Merger
Controller
Feeder
Controller
Feeder
Controller
Sensors/
Actuators
Feeder
Controller
Sensors/
Actuators
Packer
Controller
Product
Information
Server
Sensors/
Actuators
Printer/
Separator
Controller
Figure 11.10: Architecture Structure Diagram
Sensors/
Actuators
Stacker
Controller
Figure 11.10 shows an example of an Architecture Structure Diagram (ASD). ASDs represent
structure at the system level. These diagrams are in general block diagrams that
show the physical and/or logical structure of a conceptual solution. Blocks are interconnected.
In general the interconnects represent a communication channel topology.
The meaning of an interconnection, however, can depend on a specific implementation.
A logical topology can represent a software structure of communicating modules. Connections
between software modules can be implemented by for instance procedure calls.
Hardware channels can become real physical channels with non-ideal properties.
11.4.4.1 Architecture Design
System level design in the form of sketches is the basis for structuring a system. Whether
this can be performed adequately depends on the problem domain. A new area of
system design will not yet be supported by classic examples of architectures. In such
a case analysis starts with a study of the problem domain. Objects can be modelled in
Message Flow Diagrams and/or Object Class Diagrams. By performing this modelling
on a rather detailed level, it is possible to create an adequate architecture structure by
grouping elements in a hierarchical structure. Preferably this is done according to a
structure of the problem domain.
Many designs are based on classic architectural approaches. The use of classic approaches
is mostly urged by the requirement of a short system development time,
available skills and experience and investments in tools and know-how.