You model the System View on a series of diagrams. System Nodes of a system, which are where system functions are performed, are modeled on an SV-1 System Interface diagram. System Functions, which are how things are performed, are modeled on SV-4 diagrams.
There are two SV-4 diagrams:
•you build a functional decomposition of System Functions and their hierarchy on an SV-4 Functional Decomposition diagram, and
•you show the flow of information between System Functions on an SV-4 Data Flow diagram.
The flow of information between System Functions on an SV-4 Data Flow diagram is accomplished using Data Flow lines. You specify what System Functions are performed on what System Nodes using a matrix (the System Function to System Node matrix, which has an intersecting cell definition of SysNodeFunction). You do not specify this information directly in the System Node definition. In fact the information is not even displayed within the System Node definition: however it can be displayed on the node symbol.) You specify one or more System Entities that perform a System Function on a System Node within the SysNodeFunction definition (the intersecting cell of the matrix).
When that information is specified, you can gain an understanding of the dependencies of System Entities to one another, and System Nodes to one another. Remember Data Flow arrows are drawn between System Functions on an SV-4 diagram, denoting information flow between System Functions. When a Function performed on a node (we will call it the target Node) needs information from another Function on another Node (we will call it the source Node) to perform its tasks, then the target Node has a System Data Exchange (SDX) that is satisfied by the source Node. In this case a System Node Interface Line should be modeled between the two Nodes to show that one passes information to the other. The name of the Data Flow line drawn between two System Functions is mapped to an SDX existing within a System Node Interface Line drawn between the two corresponding System Nodes. A System Node Interface Line has no name (or actually a hidden name of SNI; its identity is determined by the System Nodes it is attached to).
Likewise, when a Function on a Node is performed by a System Entity (we ill call it the target System Entity) needs information from another Function performed by another System Entity (we will call it the source System Entity) to perform its tasks, then the target System Entity has a System Data Exchange (SDX) that is satisfied by the source System Entity. In this case a System Interface Line should be modeled between the two System Entities to show that one passes information to the other. The name of the Data Flow line drawn between two System Functions is mapped to an SDX existing within a System Interface Line drawn between the two corresponding System Entities. A System Interface Line has no name (or actually a hidden name of SI; its identity is determined by the System Entities it is attached to).
Activity Based Method (ABM) for systems views
The Activity Based Methodology specifies a step-by-step method on how to build the SV models.
1 Specify a functional hierarchy of system functions.
•On each context SV-4 Data Flow diagram, draw external system functions.
•Decompose context-level Functions: draw data flow lines between system functions on SV-4 Data Flow decomposition diagrams. You can balance parent-child diagrams by running a balancing algorithm manually.
•Specify what each System Function does with data. Within a field of the System Function definition, they can use structured English to specify what the System Function does. Within that structured English, you can specify the pieces of data that are acted upon. Within the repository, you can specify data elements and data structures. A data element is the smallest piece of data that is captured in the underlying data dictionary. A data structure is a grouping of data elements. For example, you could create data elements such as Street Address, City, State, and Zip Code, and group them in a data structure called Address.
•Specify the data elements and data structures that flow between System Functions in the definition of each Data Flow line.
3 Build traceability between System Functions, System Nodes, and Systems (ABM for DoDAF): use System Node to System Function matrices to specify correlation between System Functions, System Nodes, and System Entities (the System Entity is specified underneath the intersecting cell of System Functions and System nodes. This is similar in concept to creating a triplet of information between operation activities, operational nodes, and roles in the Operational View).
5 Generate system data exchange, system interface, and system node interface definitions. This information is created in the repository, and you can push out a report that tells you what was created.
6 Visually view the System Node Interface lines (containing SDXs) between System Nodes, and the System Interface lines (containing SDXs) between System Entities (embedded in System Nodes).
8 Generate the SV-6 systems data exchange matrix reports to an Excel spreadsheet. This report provides the following information for each SDX: whether it is valid or invalid, the System Function, System Node and System Entity it is from, and the System Function, System Node, and System Entity it is sent to, along with the Data Flow line it was generated from, and so on.