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Context & Dataflow Diagrams. CONTEXT DIAGRAM A context diagram is a graphical method of representing using a single process together with inputs and.

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Presentation on theme: "Context & Dataflow Diagrams. CONTEXT DIAGRAM A context diagram is a graphical method of representing using a single process together with inputs and."— Presentation transcript:

1 Context & Dataflow Diagrams

2 CONTEXT DIAGRAM

3 A context diagram is a graphical method of representing using a single process together with inputs and outputs (external entities) Three symbols only exist The process; The data flow; The external entity. Entity Process

4 Entity Process Entity Data flow A context diagram

5 Student Use Search engine Student Keyword URL A context diagram Student searches the internet

6 Create a context diagram for: 1.Searching an online telephone database. 2.Use of an ATM. 3.Use self server check out.

7 DFD

8 A DFD is a graphical method of Representing a system using a number of processes together with inputs; outputs; storage.

9 Process The 4 main symbols used to show : the process; the data flow; the data store; the external entity. Database Data store External Entity

10 Customer Search Customer details Call number Call details A data flow diagram Database

11 Customer Order is processed Customer order Invoice & book Customer & order details invoice A data flow diagram Database invoice is generated and sent

12 student Use search engine Load website Database Of website keyword URL A data flow diagram search for image Project graphic

13 A video store is considering installing a self-checkout system where customers can borrow videos by scanning their membership cards and videos and pay by EFTPOS. A self-checkout transaction has three steps: membership validation; borrowing limit check; payment processing. For membership validation the barcode on the membership card is used to access the member database to find a match. The customer proceeds to the scanning of videos if the membership is valid, otherwise a message is displayed. Using the video barcode data and details from the member database, the system checks that no more than six videos are borrowed. A message is displayed if the limit is exceeded. Payment processing involves the calculation of borrowing charges, the scanning of the customers EFTPOS card, the entry of a personal identification number and the electronic communication of these details to the financial institution. Video charges are obtained from the video database via the video barcodes. Transaction details are written to the transaction file for each video borrowed.

14 (i) Draw a dataflow diagram with the three processes that represents this proposed self- checkout system, ensuring that you show external entities and data stores. (Refer standards package section 2 Q.25)

15 Create a data flow diagram for the borrowing of a book. STEPS I TAKE WHEN CREATING SUCH A TOOL. 1.Decide upon the: processes, entities, dataflow storage. 2. Draw rough diagram adding the: processes, entities, dataflow storage. 3. Label as you go.

16 Create a data flow diagram for the borrowing of a book: EntityProcesses Data flow borrower Search d/b of borrowers for borrowing eligibility Borrowers details & book request Search d/b for details of requested book Information about borrower Locate book, scan book & user bar code Information about books Update borrower & book records Information about library transactions Result of d/b search Storage D/b of borrowers, books & library transactions

17 Process borrower Database 1 2 3 4 5 6 7 8 9 10 6

18 Create a data flow diagram for: 1.Searching an online telephone database. 2.Use of an ATM. 3.Use self server check out.

19 A video store is considering installing a self-checkout system where customers can borrow videos by scanning their membership cards and videos and pay by EFTPOS. A self-checkout transaction has three steps: membership validation; borrowing limit check; payment processing. For membership validation the barcode on the membership card is used to access the member database to find a match. The customer proceeds to the scanning of videos if the membership is valid, otherwise a message is displayed. Using the video barcode data and details from the member database, the system checks that no more than six videos are borrowed. A message is displayed if the limit is exceeded. Payment processing involves the calculation of borrowing charges, the scanning of the customers EFTPOS card, the entry of a personal identification number and the electronic communication of these details to the financial institution. Video charges are obtained from the video database via the video barcodes. Transaction details are written to the transaction file for each video borrowed.

20 (i) Draw a dataflow diagram with the three processes that represents this proposed self- checkout system, ensuring that you show external entities and data stores. (Refer standards package section 2 Q.25)

21

22 http://www.getahead-direct.com/gwbadfd.htm http://www.agilemodeling.com/artifacts/dataFlowDiagram.htm http://www.cems.uwe.ac.uk/~tdrewry/dfds.htm http://spot.colorado.edu/~kozar/DFDtechnique.html http://www.infoarchgroup.com/qrdfd.htm Link to dfd tutorials

23 Systems Flow Chart

24 Systems flow chart is a graphical method of representing both the flow of data and the logic of the system. It documents the essential details of the system such as sequence, processes and precise rules for selecting particular actions. The flow chart will also show the hardware used to process data, such as the peripheral devices, storage media and processing units.

25 SymbolMeaningSymbolMeaning Input/output Manual operation Paper document Magnetic tape Online display Direct access storage device Online input Flowline Punched cards Telecommunication link Process Predefined process TerminalDecision

26 begin Enter book details Library software Search results Need printout False True False True Search report Are you finished End Library database A system flow chart for finding a book in the library.

27 A system flow chart for hardware Laptop Zip drive Floppy drive CD-Rom drive Colour inkjet printer Keyboard Scanner Mouse Input ProcessingOutput modem Network connection File server Internet


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