Chapter A Flowcharts and Data Flow Diagrams

1. Chapter AFlowcharts and Data Flow Diagrams

2. Quote for The Day • Spoon feeding in the long run teaches us nothing but the shape of the spoon. • E. M. Forster

3. Purpose and Description of Flowcharts • Graphically document information systems • Summarize pages of narrative • Focus on the physical aspects of information flows • Types of flowcharts • System flowcharts show the entire system configuration, including documents, data flows, and processes • Document/Procedure flowcharts show the creation, flow, and destinations of documents and the procedures performed on them • Hardware flowcharts show the hardware configuration • Program flowcharts show the logic and processing steps of a computer program

4. Data Flow Diagrams (DFD) • Data flow diagramming symbols are used for a variety of system analysis purposes, including graphically displaying the logical flows of data through a process. • Unlike flowcharts which represent the physical components of an information system, data flow diagrams can provide a more conceptual, nonphysical display of the movement of data through a system. • Data flow diagrams disregard such things as organizational units, the computer on which the data are processed, and the media on which the data are stored. • The movement of data across offices or departments within a particular system environment are not represented.

5. (A) Process (B) Data inflow sources, information outflow destinations (C) Data store (D) Data flow lines Data Flow Diagram Symbols

6. (A) Process Data Flow Diagram Symbols • Process • Circles are used to represent processes that take data inflows and transform them to information outflows. • The circle contains two labels. • The first label is a process number and the second is a process name. • Some use rectangular boxes with rounded corners.

7. Data Flow Diagram Symbols • Data Sources and Sinks • Rectangles (or squares) represent data (inflow) sources and (information outflow) sinks • The rectangle is labeled with the name of the data source or sink/destination (e.g. Customer, Vendors, Government Agency). • The sources and sinks play an important role in the data flow diagram. • The sources and sinks are agents external to (i.e. outside the scope of) the system represented on the diagram. • They delineate the boundaries of the system. (B) Data inflow sources, information outflow destinations

8. (D) Data flow lines Data Flow Diagram Symbols • Data Flow Lines • Data flow lines display the route of data inflow and information outflow. • They can be straight or curved lines. • The data flow is generally labeled with the name of the data (e.g. a customer order, a bill, a financial analysis) and the arrow indicates the direction of the data flow.

9. (C) Data store Data Flow Diagram Symbols • Data Stores • Two parallel straight lines are used to display a store or collection of data. • Some people refer to data stores as data at rest. • A description of the data store contents is entered on the symbol. • Data stores are used anytime it is necessary to store the output from a process before sending it on to the next process. • Some use a rectangular box that is open at one end. Inventory

10. There are different categories of data flow diagrams: Data flow diagrams of the current physical system Data flow diagrams of the current logical system Data flow diagrams of the new or proposed logical system Data flow diagrams of the new proposed physical system Both logical and physical diagrams use the same set of symbols. The logical diagrams show the conceptual flow of data without including any references to the physical characteristics of the system. The physical diagrams, on the other hand, include labels that describe physical attributes of the system, such as labeling worker or job titles, department names, and the names or descriptions of the technology used to process and store the data. Data Flow Diagrams (DFD)

11. Context Diagram • Top Level - least detailed • describes the data flows into and out of the system and into and out of the external entities • external entities - persons, places, or things that are outside of the system that send data to or receive data from the system

12. Context Diagram boundary customer payment interface Cash receipts process deposit Bank Relevant environment

13. Physical Data Flow Diagram • Shows a system’s internal and external entities, and the flows of data into and out of these entities • Internal entities - person, place or thing within the system that transforms data - must be able to transform data • e.g. clerk, departments, computers • Specifies where, how, and by whom a system’s process are accomplished. • Does not tell what is being accomplished • Figure 3.3

14. Physical Data Flow Diagram • Circles are labeled with nouns, defines internal entities • Boxes indicate external entities • Arrows (flows) are labeled to show how data are transmitted • Parallel lines indicate where data is stored

15. Logical Data Flow Diagram • Shows a system’s processes and the flows of data into and out of the processes • Used to explain what tasks the system is doing without having to specify how, where, or by whom the tasks are accomplished • What a system is doing will change less over time than will how it is doing it. • E.g. cash receipt system will typically receive customer payments and post them to the customer’s account; however, the form of the payment--cash, check, electronic funds--and the methods of recording--manual, computer--may change

16. Logical Data Flow Diagram • Concentrate on the functions that a system performs • Circles are labeled with verbs that describe the action being performed • Flows describe the nature of the data - not how the data are transmitted • Subsequent level - provides more detail • ZERO - shows only very high level processes • decomposition - dividing processes into more detailed

17. Constraints: General Rules • All processes should have unique names. If two data flow lines (or data stores) have the same label, they should both refer to the exact same data flow (or data store). • The inputs to a process should differ from the outputs of a process. • Any single DFD should not have more than about seven processes.

18. Constraints: Process Rules Incorrect • No process can have only outputs. (This would imply that the process is making information from nothing.) If an object has only outputs, then it must be a source. • No process can have only inputs. (This is referred to as a “black hole”.) If an object has only inputs, then it must be a sink. • A process has a verb phrase label. Correct Incorrect Correct Edit

19. Yes Constraints: Data Store • Data cannot move directly from one data store to another data store. Data must be moved by a process. • Data cannot move directly from an outside source to a data store. Data must be moved by a process that receives data from the source and places the data in the data store. • Data cannot move directly to an outside sink from a data store. Data must be moved by a process. • A data store has a noun phrase label. No No Yes No Yes CUSTOMER

20. Constraints: Source/Sink 11. Data cannot move directly from a source to a sink. It must be moved by a process if the data are of any concern to the system. If data flows directly from a source to a sink (and does not involved processing) then it is outside the scope of the system and is not shown on the system data flow diagram DFD. 12. A source/sink has a noun phrase label. Incorrect Correct Customer

21. Constraints: Data Flow 13. A data flow has only one direction between symbols. It may flow in both directions between a process and a data store to show a read before an update. To effectively show a read before an update, draw two separate arrows because the two steps (reading and updating) occur at separate times. 14. A fork in a data flow means that exactly the same data goes from a common location to two or more different processes, data stores, or sources/sinks. (This usually indicates different copies of the same data going to different locations.) No Yes A No B A Yes A

22. 15.A join in a data flow means that exactly the same data comes from any of two or more different processes, data stores, or sources/sinks, to a common location. 16.A data flow cannot go directly back to the same process it leaves. There must be at least one other process that handles the data flow, produces some other data flow, and returns the original data flow to the originating process. 17.A data flow to a data store means update (i.e., delete, add, or change). 18.A data flow from a data store means retrieve or use. 19.A data flow has a noun phrase label. More than one data flow noun phrase can appear on a single arrow as long as all of the flows on the same arrow move together as one package. Constraints: Data Flow

23. Uses for DFDs • Explore the functions of a system - facilitates understanding a complex system • Define the scope of a system development project • What will and what will not be part of the system to be developed. • Physical DFDs - describe a system’s players and tell who gets what data and how many times they get the data - help find the source of a system’s backlogs or inefficiencies • Logical DFDs - develop a new or modified information system

24. Basic Elements of System/Document Flowcharts • May draw freehand or with a template • Software packages - Visio, PowerPoint, Designer • Three simple graphical elements may be combined to represent various types of physical information flows and processes • Symbols Flow lines Areas of responsibility Cashier Dept A Bank

25. Customer Document Flow in a Manual System Employee involved Accounting department in the transaction Record transaction journal entry Transaction Journal Start General Ledger Prepare source document Post Journal entries to sub.ledger Adjust and close ledger Prepare financial statements Recorded document 3 Source Document 1 2 3 Financial Statements Trial Balance Subsidiary Ledger N Investors/ Creditors N= numeric N

26. Sales Clerk Accounts Receivable Clerk Cash Receipts Clerk From Customer 1 2 Start Payment Remittance Advice Invoice N Prepare Sales Invoice Check customer credit Endorse check prepare remittance advice Record transaction and update ledger Transaction Journal Sales Invoice 1 2 3 Remittance advice 1 2 Accounts Receivable Ledger 3 1 N 2 Customer N Customer N Sales/Collection Document Flowchart N= numeric

27. 1 Shipping Receipt Invoice Ledger 2 3 (A) Single Document (B) Non-Processed Document 4 (C) Overlapping symbols- same document 4 Sales Invoice Sales Order 3 2 Invoice (D) Two overlapping symbols - same document (E) Two overlapping symbols - different documents Flowchart Symbols: Documents

28. (A) On-line Manual Device (B) Terminal Display (C) I/O (Input/Output) (D) Manual Process (E) On-line Computer Process N A Permanent File Temporary File (F) Off-line or Noncomputer Process (G) Off-line Paper File (H) On-line Data Storage (I) Disk Storage (J) Magnetic Tape Storage Flowchart Symbols

29. on page 2: 1 To Customer p.4 to page 4 connector #1 Indicates the flow will continue at the on-page connector #1 1 Start on page 4: 1 1 From Bank connector #1 from page 2 Indicates where the flow continues from the on-page connector #1 (B) Start (or end) Process p.2 (C) On-page Connectors (A) Enter/Exit System (D) Off-page Connectors ---------------- (E) Annotation (F) Decision (G) Calculator/ Register Tape (H) Physical Object (I) Flow Lines (J) Communication Link Flowchart Symbols

30. Flowchart Element 2: Flow Lines • Flow lines are used to connect the symbols on the document flow chart. • A solid line indicates the flow of a document or object • A dotted or dashed symbol indicates a flow of information rather than the physical document • Arrows are used when the documents or information flow is not left-to-right or top-to-bottom • Some flowcharts also show communication flows such as by telephone modem or satellite

31. Flowcharting Element 3: Area of Responsibility • Areas of responsibility are displayed to enable the flowchart reader to clearly identify changes in responsibility as the documents flow through the system. • They are represented on flowcharts by segmenting and labeling columns. • Areas of responsibility may be departments, sections within a department, or individual employees within a department. • Judgment must be used in choosing the level of subdivision that one column should represent.

32. Left-to-right, Top-to-bottom All documents must have an origin and termination indicate origin by darkening one corner of the symbol each copy of the document must flow to a permanent file symbol a symbol denoting an exit from the system, or an off-page connector a document destruction symbol (small black box) “cradle to grave” documentation Keep flowcharts uncluttered place areas with frequent interchange in adjacent columns enter narrative only in symbols Make sure progress of a document is clear. Diagram a document before and after each process entering or leaving a file entering or leaving a page or area of responsibility Make sure the flowchart is complete Preparation Conventions

33. Hardware flowcharts show the hardware configuration of a system. The same symbols are used, but they are used to represent physical pieces of computer hardware. the document symbol - printer, the magnetic tape symbol - tape drive, a disk symbol - disk drive, a computer process symbol - central processor, and an off-line process symbol - auxiliary hardware like an optical character reader. The type of hardware is recorded on the face of the symbol. Program flowcharts depict the detailed logic of a computer program. Only five symbols are used in program flowcharting: Input/Output (see C on Exhibit A-4), Process (see E on Exhibit A-4), Decision (see F on Exhibit A-5), Start/End (see B on Exhibit A-5), and Flow lines (see I on Exhibit A-5). As always, a description of the logic is recorded on the face of the symbol. The Basic Elements of Hardware and System Flowcharts

34. The flowchart is one of the easier types of documentation for information customers and management to understand. Often, auditors use system, document, and procedure flowcharts to understand business and systems controls in an environment The primary weakness of the flowchart is that it is tied to physical information flows and system characteristics that hide the procedural essence of the system. Some flowcharts are full of data and processing artifacts because they are tied to an outdated information technology. Summary

35. Uses for Flowcharts • Used to document and analyze controls