Chapter Eight

Balancing The conservation of inputs and outputs to a data flow diagram process when that process is decomposed to a lower level.
Context diagram An overview of an organizational system that shows the system boundary, external entities that interact with the system, and the major information flows between the entities and the system. See also Data flow diagram.
Data flow diagram A picture of the movement of data between external entities and the processes and data stores within a system.
Data store Data at rest, which may take the form of many different physical representations.
DFD completeness The extent to which all necessary components of a data flow diagram have been included and fully described.
DFD consistency The extent to which information contained on one level of a set of nested data flow diagrams is also included on other levels.
Decomposition See Functional decomposition.
Functional decomposition An iterative process of breaking the description of a system down into finer and finer detail which creates a set of charts in which one process on a given chart is explained in greater detail on another chart.
Level-0 diagram A data flow diagram that represents a systemâs major processes, data flows, and data stores at a high level of detail.
Level-n diagram A DFD that is the result of n nested decompositions of a series of subprocesses from a process on a level-0 diagram.
Primitive DFD The lowest level of decomposition for a data flow diagram.
Process The work or actions performed on data so that they are transformed, stored, or distributed.
Source/sink The origin and/or destination of data, sometimes referred to as external entities.

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