2 Managerial mapping tools Budgets, financial reportsArchitectural and geographical blueprints and mapsFlowchartsTimelines, Gantt and Pert chartsMission statementsOrganizational charts
3 Understanding & documenting processes Entity-relationship modelsShow logical structure of data needed to support business processData flow diagramsShow what is doneFlowchartsShow how it is done
4 Information System Analysis & Design 2 keys to Information System Development:* Entity-Relationship Model - analysis anddesign of information structure in a system.* Data Flow Diagram - analysis and designof the information flow (actually more of thebusiness processes) in a system.Concept behind this traditional approach:Procedure + Data Structure = Program
11 Environmental elements External elements are those that exist outside the boundaries of the system.They can be persons, organizations, or other systems.In a way, they serve to define the system’s boundary.
12 Data FlowsData flows are any collection of logically related data elements that travel from one process to another. They can be of any size.Think of a record, a note, a phone call, a letter, or a file.Data flows can converge or diverge, they can be one or two way flows.
13 Processes Processes are transformations of inputs into outputs. It is best to label each process as verb, or verb + object.
14 Data StorageData stores hold data (while flows are about data-in-motion).
15 Leveled Data Flow Diagrams Context level diagramLevel 0 diagram (“top level”)Level n figures (diagrams)pyramid, granularity.How deep?Structured English, pseudocode, flowcharts?
16 Steps to develop DFD (1) Conceptualize data flows from top down– 1. Make a list of business activities and use it todetermine various:external entities, data flows, processes, data stores.2. Create a Context Diagram: with externalentities and data flows to and from the system- which is the only process, labeled as #0.The Context DFD should not have any datastores, nor any detailed processes.3. Draw the next level DFD - Diagram 0.
17 Steps to develop DFD (2) 3. Draw the next level DFD Œ Diagram 0. It should show major business processes andpossible data stores at this level.4. Create a Child Diagram for each process inDiagram 0, exploding if necessary.5. Check for errors and designate good names.6. Use the DFD to reason about improving theoperation by re-organizing business processes.
18 Context level diagrams Use only a single process modelProcess represents entire systemNo numbersAll external entitiesShow all in- and outflows of info
19 “Figure “n” diagramsEach level “explodes” one process on preceeding levelEach level numbered for process it explodesInclude up to seven processes on single diagramStopping rule?
21 Diagramming guidelines Label each data flow: use unique namesKeep data flow names constant across levelsAvoid (diagnose) read-only processesWrite-only processes are only allowed under one condition...
22 Creating Diagram 0 1. Start with input from an external entity: What happens to this data entering the system?Is it stored?Is it input for several processes?2. Work backwards from output data flow:Where does this data come from?Is it calculated on demand, or was it stored in a file?3. Examine data flow to and from a data store:Which processes put data into the store?Which processes use the data?Which processes are responsible for update?
23 Whither and Why DFDs? (Most?) Natural way to document a system Simple, common communicationSimple, common languageSupported by- and support the creation of CASE
24 Accounts Payable Problem Consider the following scenario.Each month you receive bills from various vendors (e.g., phone, auto insurance, credit cards, utilities) and periodically other billings (e.g., magazine subscriptions, university tuition and fees). Consider all of these billings as being examples of invoices from vendors. Like most people you don't pay your bills on the same day that they are received but rather review each invoice and prioritize them in terms of which you will pay first. These reviewed and prioritized invoices are then placed in an old shoe box until you decide you had better start paying some of them.You remove an invoice from the shoe box and prepare a check to be mailed to the vendor. You check the old balance in your check register and update the register with the check information and compute a new balance. You may do this several times a month.At the end of the month you receive a statement from your bank that lists the checks that have cleared your account. You (should) take your check register and compare your list of checks and their amounts with the statement that you received from the bank. If everything is in balance then you place an appropriate mark in your check book else you enter a correcting entry (the bank never makes a mistake).
26 Order Entry ProblemSAM's is a mail order catalogue store. A customer fills out the sales order form that is enclosed in the catalogue and mails it to their headquarters in the Bahamas (postage prepaid). Upon receipt, a clerk opens the envelopes and removes the sales order forms. The clerk gives the forms to a data entry operator, who keys the data onto a diskette using a microcomputer. After data entry, the sales orders are filed in a Sales Order History file. The diskette containing all of the sales order data is then read by a minicomputer. For each ordered item, the Inventory Master Record is retrieved from the Inventory master files and the balance on-hand is reduced by the ordered amount. The updated Inventory Master Record is written back to the file. The same program prints picking tickets and writes a Daily Sales Report file onto the system disk. The picking tickets are input to the order filling system where they are used by warehouse personnel in picking the merchandise from the shelves for shipment to the customers. Another minicomputer program reads the Daily Sales Report file and prepares a daily sales report that goes to the sales manager.
27 Sales Order (SO) DFD Process Sales Order Context Diagram Sales Order 1.0Open MailCustomerCustomerSalesOrderSales Order Form2.0Enter OrderEnteredSales OrdersSales OrderHistory FileProcessSalesOrderEnteredSalesInventory Master Recordsto be updated3.0UpdateInventoryMaster FileDailySalesReportInventoryMaster FilePickingTicketsUpdatedInventory Master RecordsOrderFillingStationDailySalesSalesManagerOrderFillingStationPickingTickets4.0Print DailySales ReportContext DiagramSalesManagerDaily Sales Report
28 Prepare Check Flowchart for AP 2.0 StartRemove next billGet balanceBalanceGT Bill?NoYesWrite CheckReturnbill to boxUpdate Register```YesMoreBills?NoStop
29 Open Mail Flowchart for SO 1.0 StartStartOpen MailOpen MailRemove Sales OrderRemove Sales OrderPlace in PileTakeS.O. toOperator```YesMoreMail?```YesMoreMail?Takepile toOperatorNoStopStop