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.
