Data Flow Diagram
Using Data Flow Diagrams
Data flow diagram is used by system analyst to put together a graphical representation of data processes throughout the organization. It depicts the broadest possible overview of system inputs, processes, and outputs. A series of layered data flow diagrams may be used to represent and analyze detailed procedures in the larger system.
By using combinations of only four symbols, the system analyst can create a pictorial depiction of processes that will eventually provide solid system documentation.
Advantages of the Data Flow Approach
1. Freedom from committing to the technical implementation of the system to early.
2. Further understanding of the interrelatedness of systems and subsystems.
3. Communicating current system knowledge to users through data flow diagrams.
4. Analysis of a proposed system to determine if the necessary data and processes have been defined.
Perhaps the biggest advantage lies in the conceptual freedom found in the use of the four symbols. DFDs emphasize the processing of data and the transforming of data as they move through a variety of processes.
Conventions Used in Data Flow Diagrams
Basic symbols used on DFDs:
A. A double square - is used to depict an external entity that can be send data to or receive data from the system. The external entity is also called a source and destination of data, and it is considered to be external to the system being described.
B. An arrow - show movement of data from one point to another, with the head of the arrow pointing toward the data's destination. Data flows occurring simultaneously can be depicted doing just that through the use of parallel arrows. Because an arrow represents data about a person, place or thing, it too should be described by a noun.
C. A rectangle with rounded corners - is used to show the occurrence of a transforming process. Processes always denote a change in or transformation of data; hence, the data flow leaving a
Data flow diagram is used by system analyst to put together a graphical representation of data processes throughout the organization. It depicts the broadest possible overview of system inputs, processes, and outputs. A series of layered data flow diagrams may be used to represent and analyze detailed procedures in the larger system.
By using combinations of only four symbols, the system analyst can create a pictorial depiction of processes that will eventually provide solid system documentation.
Advantages of the Data Flow Approach
1. Freedom from committing to the technical implementation of the system to early.
2. Further understanding of the interrelatedness of systems and subsystems.
3. Communicating current system knowledge to users through data flow diagrams.
4. Analysis of a proposed system to determine if the necessary data and processes have been defined.
Perhaps the biggest advantage lies in the conceptual freedom found in the use of the four symbols. DFDs emphasize the processing of data and the transforming of data as they move through a variety of processes.
Conventions Used in Data Flow Diagrams
Basic symbols used on DFDs:
A. A double square - is used to depict an external entity that can be send data to or receive data from the system. The external entity is also called a source and destination of data, and it is considered to be external to the system being described.
B. An arrow - show movement of data from one point to another, with the head of the arrow pointing toward the data's destination. Data flows occurring simultaneously can be depicted doing just that through the use of parallel arrows. Because an arrow represents data about a person, place or thing, it too should be described by a noun.
C. A rectangle with rounded corners - is used to show the occurrence of a transforming process. Processes always denote a change in or transformation of data; hence, the data flow leaving a