Flowcharting and Data Flow Diagrams

1. Flowcharting and Data Flow Diagrams Supplemental Chapter A

2. Objectives • The objective of this supplement is to introduce you to two types of documentation tools: • Flowcharts and • Data Flow Diagrams • You should be able to: • Understand and prepare flowcharts describing the information system and procedures used in the system • Understand and prepare data flow diagrams depicting the logic of the system

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. 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

5. 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

6. 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

7. 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

8. (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

9. 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

10. 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

11. 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.

12. 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

13. 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

14. 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

15. 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.

16. 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)

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

18. (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 (explained later) and the second is a process name. • Some use rectangular boxes with rounded corners.

19. 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

20. (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.

21. (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

22. 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.

23. 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

24. 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

25. 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

26. 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

27. 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

28. Context Level Diagram Events Driven System The highest level of data flow diagrams is the context diagram. A single system is represented on a context diagram and it provides the scope of the system being represented identified in a process symbol in the center of the diagram labeled with a 0. The context diagram shows one process (representing the entire system) and the sources/sinks that represent the boundaries of the system. The data flow lines into the process represent the input data to the system (provided by sources) and the data flow lines from the process represent the output information from the system (going to the sinks). External Events Customers Management Reports 0Events Driven System Investors and Creditors Internal Departments Financial Statements Internal Events

29. Event Driven Design - Level Zero System Processes Internal events (Data Flow Diagram) Record process 1.0 External events Reports Report process 3.0 Business event data Financial Statements Internal events Maintain process 2.0 External events

30. Exhibit A-9 Level Zero DFD Example 1.0Process Customer Orders DesiredInformation Order Shipping Request 2.0Deliveries to Customers Decision Makers Bill Customers Accounts Receivable Payments DesiredInformation 3.0Process Payments

31. External event: Record Sale of Merchandise Sales Invoice Data 1.2 Review Customer Credit 1.1 Prepare Sales Invoice Approved Sales Invoice Data 1.3 Record Sales Event Data Sale Event Data Level One - Record Event Data

32. Factory Supervisor Accounting Payroll Clerk Factory supervisor Time cards 1 2 Time cards Time cards 1 N 2 Review time cards N Review time cards Reviewed time cards Record weekly wages Employee Earnings Records Record wages Employee Earnings Records Time card file (alpha) A A= alphabetic Version 1 Example Data Flow Diagram Example Flowchart

33. Factory Supervisor Accounting Payroll Clerk Factory supervisor Time cards 1 Time cards 1 2 2 Time cards N N Review time cards A Review time cards Key in time cards Reviewed time cards Record wages Record weekly wages Earnings Master File Employee Earnings Records Time card file (alpha) A= alphabetic Version 2 Example Data Flow Diagram Example Flowchart Errors Old Earnings Master File New Earnings Master File Time Card Data

34. Factory Supervisor Accounting Payroll Clerk Time cards 1 Time cards 1 2 2 N N Key in time cards Review time cards Record wages Employee Earnings Records Time card file (alpha) Employee Earnings Master File A Version 3 Example Data Flow Diagram Example Flowchart Factory supervisor Time cards Review time cards Reviewed time cards Record weekly wages A= alphabetic