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Documenting Information Systems INF2004F

Documenting Information Systems INF2004F. Preparing Data Flow Diagrams. Read narrative carefully - number lines and paragraphs in text Prepare table of entities and activities Draw context diagram - use DFD guidelines. DFD Guidelines.

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Documenting Information Systems INF2004F

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  1. Documenting Information Systems INF2004F

  2. Preparing Data Flow Diagrams • Read narrative carefully - number lines and paragraphs in text • Prepare table of entities and activities • Draw context diagram - use DFD guidelines

  3. DFD Guidelines • 1. Include within the system context (bubble) any entity that performs one or more information processing activities. • 2. For now, include only normal processing routines, not exception routines or error routines, on context diagrams, physical DFDs, and logical level 0 DFDs. • 3. Include on the systems documentation all (and only) activities and entities described in the systems narrative - no more, no less. • 4. When multiple entities operate identically, depict only one to represent all.

  4. Causeway Context Diagram

  5. DFD Guidelines (cont.) • 5. For clarity, draw a data flow for each flow into and out of a data store. You may, also for clarity to help you determine that you have included all necessary flows, label each flow with the activity number that gives rise to the flow or with a description of the flow. • 6. If a data store is logically necessary (that is, because of a delay between processes), include a data store in the diagrams, whether or not it is mentioned in the narrative.

  6. Causeway Current Physical DFD

  7. DFD Guidelines (cont.) • 7. Group activities if they occur in the same place and at the same time. • 8. Group activities if they occur at the same time but in different places. • 9. Group activities that seem to be logically related. • 10. To make the DFD readable, use between five and seven bubbles.

  8. Causeway Logical Level 0 DFD

  9. DFD Guidelines (cont,) • 11. A data flow should go to an operations entity square only when operations process functions (that is, work-related functions such as storing goods, picking goods from shelves, packing the customer’s order and so on) are to performed by that entity. A data flow should enter an entity bubble if the operations process entity is to perform an information processing activity. • 12. On a physical DFD, reading computer data stores and writing to computer data stores must go through a computer bubble. • 13. On a logical DFD, data flows cannot go from higher- to lower-numbered bubbles.

  10. Problem 4 – 7Lincoln Company (p.138) • Read the narrative on p. 138 • Attempt problems P 4.4- P 4.6

  11. Standard Flowchart Symbols

  12. Preparing Systems Flowcharts • 1. Divide the flowchart into columns; one column for each internal entity and one for each external entity. Label each column. • 2. Flowchart columns should be laid out so that the flowchart activities flow from left to right, but you should locate columns so as to minimize crossed lines and connectors.

  13. Common system flowcharting routines • The following slides show several common ways of showing processing using system flowcharting. • Pay particular attention to the way the columns are set up to communicate the flow of activities between processing entities.

  14. Enter document into computer via keyboard, edit input, record input

  15. User queries the computer Update sequentialdata store

  16. PREPARATION AND LATER MANUALRECONCILIATION OF CONTROL TOTALS

  17. KEY AND KEY VERIFY INPUTS

  18. Enter document intocomputer using a scanner

  19. Enter document into computer using scanner & manual keying

  20. System flowcharting guidelines (cont.) • 3. Flowchart logic should flow from top to bottom and from left to right. For clarity, put arrows on all flow lines. • 4. Keep the flowchart on one page. If you can’t, use multiple pages and connect the pages with off-page connectors. Computerized flowcharting packages will print your flowcharts only on paper that will fit in your printer!

  21. Causeway’s Systems Flowchart • The systems flowchart for Causeway follows on the next slide • This flowchart for causeway is without an enterprise database

  22. System flowcharting guidelines (cont.) • 5. Within each column, there must be at least one manual process, keying operation, or data store between documents. That is, do not directly connect documents within the same column. • 6. When crossing organizational lines (one column to another), show a document at both ends of the flow line unless the connection is so short that the intent is unambiguous.

  23. System flowcharting guidelines (cont.) • 7. Documents or reports printed in a computer facility should be shown in that facility’s column first. You can then show the document or report going to the destination unit. • 8. Documents or reports printed by a centralized computer facility on equipment located in another organizational unit ( warehouse, shipping dept.) should not be shown within the computer facility.

  24. System flowcharting guidelines (cont.) • 9. Processing within an organizational unit on devices such as a PC or computerized cash register should be shown within the unit or as a separate column next to that unit, but not in the central computer facility column. • 10. Sequential processing steps (computerized or manual) with no delay between them (and resulting from the same input) can be shown as one process or as a sequence of processes.

  25. System flowcharting guidelines (cont.) • 11. The only way into a computer data storage unit is through a computer processing rectangle. • 12. A manual process is not needed to show the sending of a document. The sending of the document should be apparent from the movement of the document itself. • 13. Do not use a manual process to file a document. Just show the document going in to a file.

  26. Causeway’s Systems Flowchart • The systems flowchart for Causeway is presented again on the next slide • This flowchart for causeway is again presented without an enterprise database

  27. Documenting Enterprise Systems • Moving from a file-based system to an enterprise database changes the system flowchart • An enterprise database replaces transaction and master data • Other flows may change depending on the system implementation

  28. Causeway’s Systems Flowchart • The systems flowchart for Causeway follows on the next slide • This flowchart for causeway is with an enterprise database

  29. Problem P 4-7 p. 142 • Construct a systems flowchart based on the Lincoln Company narrative

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