Filter
Top Products
80 Model Driven Systems Development with Rational Products
Localities
Here we consider the importance of localities in relation to systems engineering.
MDSD Step 12: Developing a locality model
The logical viewpoint is useful for reasoning about system functionality,
segmentation, element interaction, collaboration and interfaces at various model
and decomposition levels. The distribution viewpoint is needed to reason about a
different set of concerns. In virtually every system, we need to reason about
where functionality should be deployed, not just what functionality should be
implemented. Distributing the system elements and their functions involves
concerns such as space, time, and communication pathways. Decisions made
here affect performance, maintainability, reliability, and cost.
Localities and systems engineering
In systems engineering, the physical resources are a part or aspect of the
system. It follows that semantics need to be provided to reason about the
properties of the elements of the physical realization of the system. More
specifically, the outcome of a systems engineering effort includes a detailed
specification of the hardware to be built or acquired. Note that systems
engineering does not include the hardware engineering disciplines (mechanical,
electrical) but does include sufficient specification to be used as input to the
hardware design team.
As we have discussed, MDSD uses an analysis level, distribution viewpoint
diagram called
system locality view. In the distribution viewpoint, the system is
decomposed into elements that host the logical subsystem services. Locality
diagrams are the most abstract expression of this decomposition. They express
where processing occurs without tying the processing locality to a specific
geographic location, or even the realization of the processing capability to
specific hardware. Locality refers to proximity of resources, not necessarily
location, which is captured in the design model. For example, a locality view
might show that the system enables processing on a space satellite and a
ground station. The processing hosted at each locality is an important design
consideration.
The locality diagrams show the initial partitioning, how the system's physical
elements are distributed, and how they are connected. The term locality is used
because locality of processing is often an issue when considering primarily
nonfunctional requirements.