Data Flow Diagram - DFD Levels, Symbols, Case Study, Tutorial, Example,

Reasons for Partitioning Data Flow Diagram: 1.Different user groups: Are the processes performed by several different user groups, often at different physical locations in the company? If so, they should be partitioned into different computer programs. 2.Timing: Processes that execute at different times must be in separate programs 3.Similar tasks: May be included in the same program 4.Efficiency: Several batch processes may be included in the same program for efficiency 5.Consistency: Several processes may be included in the same program or job stream for consistency of data. 6.Security: May be partitioned into different programs for security reasons.

Creating the Context Diagram : The highest level in a data flow diagram Contains only one process, representing the entire system The process is given the number 0 All external entities, as well as Major data flows are shown Drawing Diagram 0: The explosion of the context diagram May include up to nine processes Each process is numbered Major data stores and all external entities are included Start with the data flow from an entity on the input side Work backwards from an output data flow Examine the data flow to or from a data store Analyze a well-defined process Take note of any fuzzy areas Data Flow Diagram Levels: Data flow diagrams are built in layers The top level is the Context level Each process may explode to a lower level The lower level diagram number is the same as the parent process number Processes that do not create a child diagram are called primitive Creating Child Diagrams: Each process on diagram 0 may be exploded to create a child diagr...