The executive structure supports the system's functional model. Later in the design process, functional elements are mapped to executive elements. There must be at least one executive host/correspondence for each mapped functional element.
The executive structure model is composed of structural and communications elements. Inter-related processors and shared memories communicate with two kinds of relations (communication links): communication nodes and signals.
A processor is a physical processing unit capable of executing functions. There are two kinds of processors: software (typically a programmable microprocessor/microcontroller running a real-time operating system) and hardware (typically an ASIC or FPGA).
Shared memories represent non-volatile data storage areas.
Communication nodes represent processor-to-processor and processor-to-memory communication links of three kinds: point-to-point (e.g. serial or parallel link), bus or router.
Signals are inter-processor synchronization events (typically an interrupt).