1 / 12

Data Flow Diagrams

Data Flow Diagrams. OWDA SHAQALIH. Common Errors in DFDs. Forgetting to include a data flow or pointing an arrowhead in the wrong direction Connecting data stores and external entities directly to each other Incorrectly labeling processes and/or data flow. Common Errors in DFDs.

rainer
Download Presentation

Data Flow Diagrams

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Data Flow Diagrams OWDA SHAQALIH

  2. Common Errors in DFDs • Forgetting to include a data flow or pointing an arrowhead in the wrong direction • Connecting data stores and external entities directly to each other • Incorrectly labeling processes and/or data flow

  3. Common Errors in DFDs • Including more than nine processes on a DFD (not recommended) • Omitting data flow • Creating unbalanced decomposition in child diagram • each child diagram should have the same input and output data flow as the parent process • exception: minor output such as error lines

  4. Logical vs. Physical DFDs • DFDs are categorized as either • logical • physical • Logical DFDs • not concerned about how the system is or will be constructed • Physical DFDs • show how the system is or will be constructed

  5. Progression of Models Current Logical DFD New Logical DFD New Physical DFD

  6. Advantages of Logical DFDs • Better communication with users • More stable systems • Better understanding of the business by analysts • Flexibility and maintenance • Elimination of redundancies and easier creation of the physical model

  7. Advantages of Physical DFDs • Clarifying which processes are manual and which are automated • Describing processes in more detail than logical DFDs • Sequencing processes that have to be done in a particular order • Identifying temporary data stores • Specifying actual names of files and printouts • Adding controls to ensure the processes are done properly

  8. Partitioning DFDs • The process of analyzing a DFD and deriving a series of manual procedures and computer programs • A dashed line is drawn around a group of processes that are included in each computer program or manual procedure

  9. Why Partition ? • Different user groups should have different programs • Processes that execute at different time must be in separate programs • Similar tasks may be included in the same program • Several batch processes may be included in the same program for efficiency

  10. Why Partition ? • Several processes may be included in the same program or job stream for consistency of data • Processes may be separated into different programs for security

  11. Purposes of DFDs • Unexploded DFDs are useful to identify information requirements • Exploded DFDs can be used for • presentation • education • gathering feedback information from users

  12. Uses of DFDs • Used to analyze the system to ensure that the design is complete • Used to partition the system into programs • Used for system documentation

More Related