Systems Documentation Techniques

1. Systems Documentation Techniques Professor Merle Martin Professor Yan Xiong College of Business CSU Sacramento 2/6/023

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 level • Ease 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 modules • until they fit into the human mind • solving the modular sub-problems • aggregating small solutions into total solution

5. Agenda • Why Document Accounting Information Systems • Data Flow Diagrams (DFDs) • Flowcharts • Difference between DFD

6. Data Flow Diagrams • Data flow diagram (DFD) graphically describes flow of data within any system • Used to document existing systems and to plan and design new ones • No ideal way to develop a DFD • judgment within standard rules

7. Data Flow Diagrams • DFD composed of only four elements: • Data sources and destinations: External Entities • Another organization/organization unit which exchanges data with the focal system • A person who interacts with the system (customer of a banking system) • Another information system • Data Flows • Processes • Data Stores: Temporary or permanent repository of data

8. DFD Symbols INPUT PROCESS OUTPUT Process Data Flow Data Flow External Entity External Entity Source Sink Data Flow Data Store

9. Payment deposit Customer Bank Source Sink Remittance data Customer File DFD Symbols 1.1 Process Payment

10. Data Flow Diagrams Explosion • Data flow diagrams subdivided into successively lower levels in order to provide increasing amounts of detail • This decomposition process is called “explosion”

11. Data Flow Diagram Explosion • Context Level • Ist Level Explosion • 2nd Level Explosion • Succeeding levels as necessary • Until reach primitive level • Ready to code

12. Context Diagram • Includes only • External Entities • Data Flows • All elements included on Context Diagram mustbe included somewhere on lower level diagrams • Data stores rarely included!

13. Context Diagram • Why discourage Data Stores on Context Diagram? • Author includes them • Context Diagram shows interaction of your system with outside world • Data Stores are INSIDE your system, not in outside world

14. Purchase Requisition Purchase Order Vendor Inventory System Order Entry System Receiving System Special Order Purchase Order Notification 0 Purcha- sing Context Diagram

15. 1st Level Explosion • Also includes all data flows and external entities • Now data stores are added • Excellent means of confirming understanding of system between analyst and client • Each process will be explodedinto lower level DFDs

16. Purchase Requisition Inventory Order Entry Vendor Receiving Ist Level Explosion Status Inventory 1 Edit Order Problems Special Order Problem Orders Approved Order 2 Set Ship Mode Info Purchase Order Vendor Draft P.O 3 Prepare P.O. P.Order P.O.Noti- fication P.O. Copy

17. 2nd and Succeeding Levels • Must be consistent with parent DFD • Same external entities • Same data stores • Same data flows

18. 2nd Level Explosion (Process 1) Purchase Requisition 1.1 Log-in Order Inventory Special Order Inventory Logged-in Order Order Entry 1.2 Edit Order Status Next # Problem Orders Problems Log-in #s Edited Order 1.3 Approve Order Process 2.1 Approved Order

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 Store D. 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 Flow J. 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 Flow L. A data flow cannot go directly back to the same process it leaves M. A data flow to a data store means update (delete or change) N. A data flow from a data store means retrieve or use O.Noun phrase label

24. Other DFD Issues • Two additional guidelines • Inputs to a process are different from outputs of that process • Every 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 • Flowchart • Difference between DFD and Flowchart

27. Flowcharts • A 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 Symbols • Flowcharting symbols can be divided into the following four categories: • Input/output symbols • Processing symbols • Storage symbols • Flow and miscellaneous symbols

29. Document Online keying Display Input/output; Journal/ledger Flowcharting Symbols: Input Output Symbols Symbol Name

30. Manual operations Computer processing Auxiliary operation Flowchart Symbols: Processing symbols Symbol Name

31. Magnetic disk Magnetic tape Flowchart Symbols: Storage Symbols Symbol Name

32. Document or processing flow On-page connector Off-page connector Terminal Decision Flowchart Symbols: Flow and miscellaneous Symbols Name Symbol

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 ComputerSystem Flowcharts? • Systemflowcharts 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 ComputerSystem Flowcharts? • The resulting new information is the output component. • System flowcharts are an important tool of system analysis, design, and evaluation.

36. Output What are ComputerSystem Flowcharts? Input Process Storage

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. If a condition is met What are Program Flowcharts? Input data No Yes Perform calculation Update 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. Start Approved for credit? Inventory available? Stop Flowchart for ProcessingCredit Orders Enter sales order Reject order No Yes Back- order No Yes Fill order

41. Example-Flowcharts • The 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 • Flowchart • Difference 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.