Context & Dataflow Diagrams

CONTEXT DIAGRAM

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. Process Entity

Entity Data flow Process Data flow Entity A context diagram

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

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

DFD DFD DFD DFD DFD DFD DFD DFD

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

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

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

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

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

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 customer’s 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.

(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)

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

Search d/b of borrowers for borrowing eligibility Create a data flow diagram for the borrowing of a book: Entity Processes 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

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

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

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 customer’s 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.

(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)

Link to dfd tutorials 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

Systems Flow Chart

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.

Symbol Meaning Input/output Manual operation Paper document Magnetic tape Online display Direct access storage device Online input Flowline Punched cards Telecommunication link Process Predefined process Terminal Decision

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

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