Presentation on theme: "Systems Documentation Techniques"— Presentation transcript:
1 Systems Documentation Techniques Professor Merle MartinProfessor Yan XiongCollege of BusinessCSU Sacramento2/6/023
2 Agenda Why Document System Data Flow Diagrams Flowcharts Difference between DFDs and Flowcharts
3 Why Document Systems? User confidence that you understand system Successive refinement of detail down to programming levelEase of Program Maintenance, System Modification, Reengineering, and Replacement
4 Why Document Systems? Problem Solving Humans solve complex problems by breaking them into smaller and smaller modulesuntil they fit into the human mindsolving the modular sub-problemsaggregating small solutions into total solution
5 Agenda Why Document Accounting Information Systems Data Flow Diagrams (DFDs)FlowchartsDifference between DFD
6 Data Flow DiagramsData flow diagram (DFD) graphically describes flow of data within any systemUsed to document existing systems and to plan and design new onesNo ideal way to develop a DFDjudgment within standard rules
7 Data Flow Diagrams DFD composed of only four elements: Data sources and destinations: External EntitiesAnother organization/organization unit which exchanges data with the focal systemA person who interacts with the system (customer of a banking system)Another information systemData FlowsProcessesData Stores: Temporary or permanent repository of data
8 DFD Symbols INPUT PROCESS OUTPUT Process Data Flow Data Flow External EntityExternalEntitySourceSinkDataFlowDataStore
9 DFD Symbols Source Payment Sink deposit Remittance data Customer Bank 1.1ProcessPaymentCustomerSourcePaymentBankSinkdepositCustomerFileRemittance data
10 Data Flow Diagrams Explosion Data flow diagrams subdivided into successively lower levels in order to provide increasing amounts of detailThis decomposition process is called “explosion”
11 Data Flow Diagram Explosion Context LevelIst Level Explosion2nd Level ExplosionSucceeding levels as necessaryUntil reach primitive levelReady to code
12 Context Diagram Includes only External Entities Data Flows All elements included on Context Diagram must be included somewhere on lower level diagramsData stores rarely included!
13 Context Diagram Why discourage Data Stores on Context Diagram? Author includes themContext Diagram shows interaction of your system with outside worldData Stores are INSIDE your system, not in outside world
14 Context Diagram Purcha- sing Inventory System Purchase Requisition VendorPurchaseOrderPurcha-singOrderEntrySystemSpecialReceivingSystemPurchaseOrderNotificationContext Diagram
15 1st Level Explosion Also includes all data flows and external entities Now data stores are addedExcellent means of confirming understanding of system between analyst and clientEach process will be exploded into lower level DFDs
16 Ist Level Explosion Inventory Order Entry Vendor Receiving Status PurchaseRequisition1EditOrderReceivingVendorOrderEntryInventoryProblemsSpecialOrderProblemOrdersApprovedOrder2Set ShipModeInfoPurchaseOrderVendorDraft P.O3PrepareP.O.P.OrderP.O. CopyP.O.Noti-fication
17 2nd and Succeeding Levels Must be consistent with parent DFDSame external entitiesSame data storesSame data flows
19 DFD Rules -- Process A. No process can have only outputs (a miracle) B. No process can have only inputs (a black hole)C. Verb phrase labels
20 DFD Rules -- Data StoreD. Data cannot move directly from one data store to another data store -- it must be moved by a process.E. Data cannot move directly from an outside source to a data store -- it must be moved by a process.F. Data cannot move directly to an outside sink from a data store -- it must be moved by a process.G. Noun phrase label
21 DFD Rules -- Source / Sink Data cannot move directly from a source to a sink. It must be moved by a process.Noun phrase label
22 DFD Rules -- Data FlowJ. A data flow has only one direction of flow between symbols; a data flow may flow in both directions to and from a data store (usually two symbols)K. A fork in a data flow means that exactly the same data goes to two different processes or data stores.
23 DFD Rules -- Data FlowL. A data flow cannot go directly back to the same process it leavesM. A data flow to a data store means update (delete or change)N. A data flow from a data store means retrieve or useO.Noun phrase label
24 Other DFD Issues Two additional guidelines Inputs to a process are different from outputs of that processEvery process in a DFD has a unique name
25 Exercise Draw a Context Diagram and a 1st level explosion Current System Description for the payroll system at No-Wear Products.Time data are recorded in each department using time cards and clocks.The time data are sent to the payroll by different departments.Payroll clerks review the time data for their completeness.Human resources send the payroll data on personnel changes, such as increases in pay rates and new employees.Payroll clerks update the payroll file based on these changes.At the end of the period, payroll clerks enter the time card data into the payroll file for processing. The payroll supervisor reviews the file and makes necessary corrections.Payroll clerks send the direct payments to the bank and also the direct deposit slips to the departments.
26 Agenda Why Document Accounting Information Systems Data Flow Diagrams FlowchartDifference between DFD and Flowchart
27 FlowchartsA flowchart is an analytical technique used to describe some aspect of an information system in a clear, concise, and logical manner.Flowcharts use a standard set of symbols to pictorially describe transaction processing procedures.
28 Flowchart SymbolsFlowcharting symbols can be divided into the following four categories:Input/output symbolsProcessing symbolsStorage symbolsFlow and miscellaneous symbols
32 Flowchart Symbols: Flow and miscellaneous Symbols NameSymbolOn-page connectorOff-page connectorTerminalDecisionDocument or processing flow
33 What are Document Flowcharts? A document flowchart illustrates the flow of documents and information between areas of responsibility within an organization.A document flowchart is particularly useful in analyzing the adequacy of control procedures.Flowcharts that describe and evaluate internal controls are often referred to as internal control flowcharts.
34 What are Computer System Flowcharts? System flowcharts depict the relationship among the input, processing, and output of an AIS.A system flowchart begins by identifying both the inputs that enter the system and their origins.The input is followed by the processing portion of the flowchart.
35 What are Computer System Flowcharts? The resulting new information is the output component.System flowcharts are an important tool of system analysis, design, and evaluation.
36 What are Computer System Flowcharts? InputProcessStorageOutput
37 What are Program Flowcharts? A program flowchart describes the specific logic to perform a process shown on a systems flowchart.A flow line connects the symbols and indicates the sequence of operations.The processing symbol represents a data movement or arithmetic calculation.
38 What are Program Flowcharts? Input dataIf a condition is metNoYesPerform calculationUpdate record
39 What are Program Flowcharts? The input/output symbol represents either reading of input or writing of output.The decision symbol represents a comparison of one or more variables and the transfer of flow to alternative logic paths.All points where the flow begins or ends are represented by the terminal symbol.
40 Flowchart for Processing Credit Orders EntersalesorderStartApprovedfor credit?RejectorderNoYesInventoryavailable?Back-orderNoYesFill orderStop
41 Prepare a system flowchart of the process described. Example-FlowchartsThe Dewey Construction Company processes its payroll transactions to update both its payroll master file and its work-in-process master file in the same computer run. Both the payroll master file and the work-in-process master file are maintained on disk and accessed directly.Data to be input to this system are keyed onto a tape using a key-to-tape encoder. This tape is then processed to update the files. This processing run also produces a payroll register on magnetic tape, employee paychecks and earnings statements, and a printed report listing error transactions and summary information.Prepare a system flowchart of the process described.
43 Agenda Why Document Accounting Information Systems Data Flow Diagrams FlowchartDifference between DFD and Flowchart
44 Differences Between DFDs and Flowcharts DFDs emphasize the flow of data and what is happening in a system, whereas a flowchart emphasizes the flow of documents or records containing data.A DFD represents the logical flow of data, whereas a flowchart represents the physical flow of data.
45 Differences Between DFDs and Flowcharts Flowcharts are used primarily to document existing systems.DFDs, in contrast, are primarily used in the design of new systems and do not concern themselves with the physical devices used to process, store, and transform data.