Introduction to Data Flow DiagramsPowerPoint PresentationParts of DFDTo Model the systemCharacteristics of DFDExplosionWhat you CAN’T do:Cougar Burger ExampleSlide 9Cougar Burger exampleIdentifying DFD partsDifferent types of DFDsDFD #1 – Order processing SystemDFD #2 – Grocery store systemDFD #3 Payroll systemIntroduction to Data Flow DiagramsWeek 6CMIS570SDLCProject Identification& SelectionProject Initiation& Planning**Analysis**Logical DesignPhysical DesignImplementationMaintenanceParts of DFDExternal Agent; Source / SinkData StoreProcessData Flow LineTo Model the systemEmphasize processIdentify, hierarchically:The systemThe subsystems/functions of the systemThe transactions within a given functionCharacteristics of DFDI-P-O modelingLeveling of DFDs (explosion)Balancing of data flowsShows flow of data not flow of controlShows set of possible paths (not what causes a path to be taken)ExplosionAlso called Functional DecompositionAn iterative process of breaking the description or perspective of a system down into finer and finer detail.Context diagram, Level 0 diagram, Level 1 diagrams, etc.Balancing the levelsWhat you CAN’T do:ProcessesNo input data flow, no output data flowData StoresData flow directly to another data storeAgentsData flow directly to another external agent, data flow directly to or from data storeData FlowsNo double arrows, no “break-off” lines defined as something different, no data flow line into another data flow lineCougar Burger ExampleContext LevelCougar Burger ExampleLevel 0Cougar Burger exampleLevel 1Identifying DFD partsBottom-up and Top-DownDFD fragmentsDifferent types of DFDsPhysicalLogicalCurrent vs NewDFD #1 – Order processing SystemWe know customers send orders to the organization and the organization sends out the products ordered with a bill for those products.Within the organization there is an order processing system.Order processing system accepts, processes, and records data about orders. The system accepts only orders if sufficient inventory exists. Inventory files and goods sold files must be updated. After the order is recorded, the customer is sent a confirmation note.DFD #2 – Grocery store systemA grocery store has just implemented a new sales system. When a customer has selected the items for checkout, the item is scanned. The system is able to identify the item scanned because of its bar code. The system looks up the price of the item from a prices file. Once all items have been identified, a total price is computed and given to the customer.DFD #3Payroll systemXYZ Corporation would like to implement a new payroll system to automate the current system. Currently, employees fill out a time record indicating the hours they worked. Gross pay is calculated based on each employees’ hourly rate and the hours they worked. Net pay is what they are actually paid after withholding deductions and taxes are taken out. Each employee receives a check with their net
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