PowerPoint PresentationSlide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10The Explosion Approach to drawing DFDs: As suggested by DeMarco and others, this diagramming technique requires the analyst to draw multiple DFDs, each one exploding from a single process on another diagram, until the system is completely modeledSlide 12TOP - DOWN analysis & functional decompositionSlide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28DATA FLOW DIAGRAMS (DFD):Sources and Sinks:–Define System BoundariesProcess (transformation)–transforms data - no detail of how the transformation is done–Inputs and Outputs–Manual / Automated–Process #, Brief descriptive label (action verb and object clause)Label(ExternalEntities)1.Receive Orders1Order Clerk:Order Entry#Desc.WhoData Store:–only processes can connect to data stores–A store is passive, process initiates flowsData Flow:# InvoicesInvoicesIdentifiers (letters,etc)NameCustomerCustomerWarehouse1.Receive Order2.Ship goods3.Collect Pmts Invoices Orders CustomersPmt. InquiriesInvoice StatementCust.Name,AddressCust.Name,AddressCust.Name,AddressShipping DetailGoods infoGoods infoInvoice DetailsOrdersInvalid OrdersBilling InfoDFD ExampleOrder DetailData Store:•may be a fundamental user requirement or an implementation store placed there for convenience.Enter OrderProcess Order(Essential Model)Validated OrderAcknowledgementOrder DetailEnter OrderProcess OrderOrdersAcknowledgementOrder Detailxxyy(Implementation Model)Update/CreateUse/RetrievalNaming data Flows:Enter orderOrdersOrders? What transformation For Essential model name should be implementation free e.g. Course Request Form vs. Form23EmployeeCreate newmember account1.Freeze accountnumber2.Generateemployeebank stat.3.AccountsReceivable DeptEmployee fileMember Accts.Modified accountstatusEmployeestatusEmployee IDand addressFrozen acct. notificationExistingaccountMembershipapplicationBank statementCommon DFD Errors•Common DFD Errors:–Process1 has inputs but produces no outputs. This is called a black hole–Process 2 produces outputs but receives no inputs. This is called a miracle–Process 3 has inputs and outputs ; however the inputs are not sufficient to produce the outputs. This is called a gray hole.DS1 DS NameE-12.0P-2E-21.0P-1DF-2DF-3DF-5DF-4DF-6DF-2DF-1DFD ErrorsPay Phone BillPhone CompanyItemized Calls Statement and InvoiceCorrect Use of Packet ConceptItemized Calls StatementInvoiceThe Data Flow Packet ConceptAuthorize Payment by Bank CardCustomerCredit Vouchers DuePaymentsCredit ReceiptAuthorize Payment by Bank CardCustomerCredit Vouchers DuePaymentsCustomer ReceiptApproved Credit VoucherSaleDiverging data flows are implementation oriented and should be avoided on essential DFDsDiverging Data FlowsThe Explosion Approach to drawing DFDs:As suggested by DeMarco and others, this diagramming technique requires the analyst to draw multiple DFDs, each one exploding from a single process on another diagram, until the system is completely modeledmThe System1.21.pn3.2.1.31.1.3.1 3.2ZZZXXXAHGZDEC MLKABBA CBDZOverview DFDContext DFD1.01.42.32.22.11.4.11.4.41.4.31.4.21.31.11.23.02.0Explodes toExplodes toExplodes toLevel 2 Diagram 1.4Level 1 Diagram 1Level 1 Diagram 2GrandchildChildChildParentFunctional Decomposition and Leveled DFDsidTOP - DOWN analysis & functional decomposition1.functionA0The System1.1Activity 1 of function ATask 1.1.1Task 1.1.2Task 1.1.31.2Activity 2 of function ATask 1.2.1Task 1.2.22.1Activity 1 of function BTask 2.1.1Task 2.1.22.2Activity 2 of function BTask 2.2.1Task 2.2.2Task 2.2.32.functionBDecomposition DiagramLevelled Set of DFDs•How many levels - not > 9 processes in single DFD•Different parts of system can have different level of detail•Consistency (Balancing) - inflow and outflow to process must correspond in next level DFD•External entities,data stores,parent processes can, but need not be repeated in child diagram•Data Stores at different levels - show data store at the highest level where it first serves as an interface between two or more processesTop- Down Analysis and Functional DecompositionCarson-Plymouth Medical Devices (CPMD), as assembler of sophisticated medical products, must maintain a ready supply of high-quality components to manufacture its products. To achieve this goal, CPMD’s purchasing department checks inventory levels each day by reviewing the inventory items stock list. When the quantity-on-hand of a particular item reaches its economic reorder point, CPMD’s purchasing department places a purchase order with its supplier (supplier data is accessed through the supplier file) for that component and files a copy in the purchase order file. When a supplier delivers a shipment along with a bill of lading, shipping and receiving (S/R) receives the shipment by performing a three-step process. First, the S/R clerk verifies the shipment by accessing a copy of the purchase order and comparing it to the bill of lading. If a received item appears on the purchase order and the bill of lading, the verified bill of lading and received items are passed on to Inspection. Otherwise, the S/R clerk generates a notice of shipment error, which is sent to the supplier.Next, the inspector inspects the valid shipment items by accessing the quality criteria, from the inspection criteria folder. If the item meets all the quality criteria, the inspector adds it to an accepted items list, which is forwarded to the inventory clerk. If an item does not pass inspection, the inspector creates a notice of defective shipment, which is sent to the supplier along with the defective items. Finally, the inventory clerk updates the inventory items list by adding the current-on-hand quantity, reflecting an updated quantity.Carson-Plymouth Medical Devices (CPMD), as assembler of sophisticated medical products, must maintain a ready supply of high-quality components to manufacture its products. To achieve this goal, CPMD’s purchasing department checks inventory levels each day by reviewing the INVENTORY ITEMS STOCK list. When the quantity-on-hand of a particular item reaches its economic reorder point, CPMD’s purchasing department places a purchase order with its supplier (supplier data is accessed through the SUPPLIER file) for that component and files a copy in the PURCHASE ORDER file. When a supplier delivers a shipment along with a bill of lading, shipping