DoDAF Viewpoints and Models
SV-4: Systems Functionality Description
The SV-4 addresses human and system functionality.
The primary purposes of SV-4 are to:
. Develop a clear description of the necessary data flows that are input (consumed) by and output (produced) by each resource. . Ensure that the functional connectivity is complete (i.e., that a resource's required inputs are all satisfied). . Ensure that the functional decomposition reaches an appropriate level of detail.
The Systems Functionality Description provides detailed information regarding the:
. Allocation of functions to resources. . Flow of resources between functions.
The SV-4 is the Systems Viewpoint model counterpart to the OV-5b Activity Model of the Operational Viewpoint.
The intended usage of the SV-4 includes:
- Description of task workflow.
- Identification of functional system requirements.
- Functional decomposition of systems.
- Relate human and system functions.
The SV-4 is used to specify the functionality of resources in the architecture (in this case, functional resources, systems, performer and capabilities). The SV-4 is the behavioral counterpart to the SV-1 Systems Interface Description (in the same way that OV-5b Operational Activity Model is the behavioral counterpart to OV-2 Operational Resource Flow Matrix).
The scope of this model may be capability wide, without regard to which resources perform which functions, or it may be resource-specific. Variations may focus on intra- or inter-resource data flows, or may simply allocate functions to resources.
There are two basic ways to depict SV-4:
- The Taxonomic Functional Hierarchy shows a decomposition of functions depicted in a tree structure and is typically used where tasks are concurrent but dependent, such as a production line, for example.
- The Data Flow Diagram shows functions connected by data flow arrows and data stores.
The Taxonomic Functional Hierarchy may be particularly useful in capability-based procurement where it is necessary to model the functions that are associated with particular capability (see SV-5).
Within an Architectural Description, the SV-4 documents system functions, the Resource Flows between those functions, the internal system data repositories or system data stores, and the external producers and consumers for the system data flows, but not those external to the Architectural Description scope. They may also show how users behave in relation to those systems.
The functions are likely to be related to Operational Activities captured in OV-5a. Although there is a correlation between the Operational Activity Model (OV-5b) and the functional hierarchy of SV-4, it need not be a one-to-one mapping, hence, the need for the Function to Operational Activity Traceability Matrix (SV-5), which provides that mapping.
Systems are not limited to internal system functions and can include HCI and GUI functions or functions that consume or produce system data. The external system data producers or consumers can be used to represent the human that interacts with the system. The System Resource 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 during development of this model (and recorded in StdV-1).
A graphical variant of the SV-4 Data Flow model may be used with swim lanes. A system swim lane may be associated with:
- A System.
- A grouping of Capabilities and System Functions (usually based on a Physical Asset).
- A Performer executing an Activity.
Swim lanes are presented either vertically or horizontally. A function can be placed in the swim lane associated with the System, Resources or Performer executing an Activity that it is allocated in the solution architecture. This provides a graphical means of presenting the interactions between Systems or Capabilities (shown through system connections on SV-1) in functional terms. This is a powerful technique for visualizing the differences between alternative solution options (which may have a common set of functions).
SV-1 Systems Interface Description
SV-2 Systems Resource Flow Description
SV-3 Systems-Systems Matrix
SV-4 Systems Functionality Description
SV-5a Operational Activity to Systems Function Traceability Matrix
SV-5b Operational Activity to Systems Traceability Matrix
SV-6 Systems Resource Flow Matrix
SV-7 Systems Measures Matrix
SV-8 Systems Evolution Description
SV-9 Systems Technology & Skills Forecast
Introduction to SV-10a, SV10b, and SV-10c
SV-10a Systems Rules Model
SV-10b Systems State Transition Description
SV-10c Systems Event-Trace Description