Product Definition. The Systems Functionality Description documents system functional hierarchies and system functions, and the system data flows between them. Although there is a correlation between Operational Activity Model (OV-5) or business-process hierarchies and the system functional hierarchy of SV-4, it need not be a one-to-one mapping, hence, the need for the Operational Activity to Systems Function Traceability Matrix (SV-5), which provides that mapping.
Product Purpose. The primary purposes of SV-4 are to (a) develop a clear description of the necessary system data flows that are input (consumed) by and output (produced) by each system, (b) ensure that the functional connectivity is complete (i.e., that a system’s required inputs are all satisfied), and (c) ensure that the functional decomposition reaches an appropriate level of detail.
Product Detailed Description. SV-4 describes system functions and the flow of system data among system functions. It is the SV counterpart to OV-5. SV-4 may be represented in a format similar to data flow diagrams (DFDs) [DeMarco, 1979]. The scope of this product may be enterprise wide, without regard to which systems perform which functions, or it may be system specific. Variations may focus on intranodal system data flow, internodal system data flow, system data flow without node considerations, function to system allocations, and function to node allocations.
The system functions documented in the SV-4 may be identified using the Service Component Reference Model (SRM),20 or some other system function taxonomy, and correlated to SV-1 and SV-2 systems. System functions are not limited to internal system functions and can include Human Computer Interface (HCI) and Graphical User Interface (GUI) functions or functions that consume or produce system data from/to system functions that belong to external systems. The external system data sources and/or sinks can be used to represent the human that interacts with the system or external systems. The system data flows between the external system data source/sink (representing the human or system) and the HCI, GUI, or interface function can be used to represent human-system interactions, or system-system interfaces. Standards that apply to system functions, such as HCI and GUI standards, are also specified in this product.
Like OV-5, SV-4 may be hierarchical in nature and may have both a hierarchy or decomposition model and a system data flow model. The hierarchy model documents a functional decomposition. The functions decomposed are system functions.