A&D - DT, DD, DFD

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A&D - DT, DD, DFD

  1. 1. Tools for Structured DesignOrganized By: Vinay Arora Assistant Professor CSED, Thapar University www.slideshare.net/aroravinay
  2. 2. Disclaimer This is NOT A COPYRIGHT MATERIAL Content has been taken mainly from the following books:System Analysis and Design Methods By Jeffrey L Whitten & Lonnie D Bentley , Analysis & Design of Information Systems By James A. Senn, System Analysis & Design By Elias M. Awad,Modern System Analysis & Design By Jeffrey A. Hoffer, Joey F.George & Joseph S. Valacich V.A. CSED
  3. 3. Tools for Structured Analysis For the Business System under Investigation DECISION & PROCEDURES are Important to System Analyst. Various TOOLS are present for Studying Operational Procedures and Decision Making Steps. TOOL – A Device, Object or Operation used to accomplish a Specific Task. Three TOOLS for Documenting Procedures: Decision Tree, Decision Table and Structured English V.A. CSED
  4. 4. Structured English STRUCTURED ENGLISH is the use of the English Language with the SYNTAX of Structured Programming. STRUCTURED ENGLISH aims at getting the benefits of both the Programming Logic and Natural Language. Program Logic helps to attain precision while natural language helps in getting the convenience of spoken Languages. Method to Overcome Problem of AMBIGUOUS Language. V.A. CSED
  5. 5. Guidelines when writing Structured English Statements should be Clear and Unambiguous Use One Line per Logical Element All LOGIC should be expressed in Operational, Conditional and Repetition Blocks Logical Blocks should be indented to show Relationship Keywords should be Capitalized V.A. CSED
  6. 6. Structured English (contd.) V.A. CSED
  7. 7. Common Keywords START, BEGIN, END, STOP, DO, WHILE, DO WHILE, FOR, UNTIL, DO UNTIL, REPEAT, END WHILE, END UNTIL, END REPEAT, IF, IF THEN, ELSE, IF ELSE, END IF, THEN, ELSE THEN, ELSE IF, CASE, EQUAL, TRUE, FALSE, AND, OR, XOR V.A. CSED
  8. 8. Developing Structured Statements Structured English uses THREE Basic Types of Statements to describe a PROCESS: SEQUENCE STRUCTURES DECISION STRUCTURE ITERATION STRUCTURES V.A. CSED
  9. 9. Sequence Structures A Single Step or Action Included in a Process. None of the Steps contains a Decision or any Conditions that determine whether the steps are taken. Operation Statements written as ENGLISH PHRASES executed from the top down. Example: 1). Pick Out a Desirable Book 2). Take the Book to the Checkout Counter 3). Pay for the Book 4). Obtain a Receipt 5). Leave the Store V.A. CSED
  10. 10. Decision Structure Another way of Showing Decision Analysis. Decision Structures occur When TWO or MORE Actions can be taken, depending on the value for a Specific Condition. After Decision Making Stated Actions or Sets of Actions for that Condition will be taken. Once Condition is made, ACTIONS are Unconditional. Keywords Like IF/THEN/OTHERWISE are used. V.A. CSED
  11. 11. Example IF a desirable book is found, THEN Take the book to the checkout counter. Pay for the book. Be sure to obtain a receipt. Leave the store. OTHERWISE Do not take the books to the checkout counter. Leave the Store. END IF V.A. CSED
  12. 12. Iteration Structure Iteration Instructions permit Analyst to Describe the cases where: Certain Activities are repeated WHILE a certain Condition Exists OR UNTIL a Condition Occurs V.A. CSED
  13. 13. Example DO WHILE Still examining more books. Read the title of the Book. IF the title sounds interesting THEN pick up the book and thumb through it. Look at the Price. IF you decide you want the book Put it in the DESIRABLE BOOK stack. ELSE Put it back on the shelf. END IF ELSE Continue END DO V.A. CSED
  14. 14. IF Desirable books are found THEN Take the books to the checkout counter. Pay for the books. Be sure to obtain a receipt. Leave the store.ELSE Do not take books to the checkout counter Leave the storeEND IF V.A. CSED
  15. 15. Tree Structure V.A. CSED
  16. 16. Decision Tree Conditions – Possible States of an ENTITY. Action – What to do when certain condition/s occur… Actions are the Alternatives. Tools used in Understanding & Matching combinations are - - Decision Trees - Decision Tables - Structured English V.A. CSED
  17. 17. Decision Tree Decision Tree – Diagram that presents CONDITIONS and ACTIONS sequentially. Shows which CONDITIONS to consider First which Second and so on. Method of showing the relationship of condition & its permissible actions. Diagram resembles branch of a TREE. V.A. CSED
  18. 18. Decision Tree – Basic Layout V.A. CSED
  19. 19. Decision Tree Sample V.A. CSED
  20. 20. Decision Tree Example V.A. CSED
  21. 21. Decision Tree (cont.) Formal Identification of Actual Decision. Force Analyst to Consider the Sequence of Decisions. Drawback of Decision Tree – A Large number of branches with many paths through them will cloud rather than aid analysis. V.A. CSED
  22. 22. Decision Tree for Invoice Processing V.A. CSED
  23. 23. Example Decision Tree – Students Data V.A. CSED
  24. 24. Example Decision Tree – Students Data – Take student as root node V.A. CSED
  25. 25. Example Decision Tree – Students Data – Take income as 2nd node V.A. CSED
  26. 26. Example Decision Tree – Students Data (contd.) V.A. CSED
  27. 27. Example Decision Tree – Students Data (contd.) V.A. CSED
  28. 28. Example Decision Tree – Students Data (contd.) V.A. CSED
  29. 29. Example Decision Tree – Students Data (contd.) V.A. CSED
  30. 30. Decision Table Decision Table – Matrix of Rows & Columns, rather than a TREE. Decision Rules are present in Decision Table. Decision Tables are a Precise yet Compact WAY TO MODEL complicated logic. Decision Tables, like If-Then-Else and Switch-Case Statements, ASSOCIATE CONDITIONS WITH ACTIONS to perform. Decision Rule – Procedure to follow when certain Conditions Exits. V.A. CSED
  31. 31. Decision Table V.A. CSED
  32. 32. Decision Table – Example Health Services V.A. CSED
  33. 33. Decision Tree - Example Longer than 10 Days Within 10 Days Over $10000 Below $5000 $5000 to $10000 Pay Full Invoice Amount Take 2% Discount from Pay Full Invoice Amount Take 3% Discount from Invoice Total Invoice Total V.A. CSED
  34. 34. Relation of Condition & Action V.A. CSED
  35. 35. Decision Table – Example Payment DiscountThere are various Formats of Decision Tables. Format doesn’t Changethe Usefulness of Decision Table. V.A. CSED
  36. 36. Building Decision Table - Steps 1- Determine most relevant factors to consider in making a DECISION. 2- Determine the most feasible steps or activities under varying conditions. 3- Study the Combinations of Conditions that are Possible. 4- Fill in the Table with DECISION Rules. 5- Mark Action entries with ‘X’ to signal action(s). 6- Examine Table for Redundant Rules. V.A. CSED
  37. 37. Decision Table –Payment Discount Example Using Yes/No Format V.A. CSED
  38. 38. Checking Decision Table Eliminating Redundancy Removing Contradictions V.A. CSED
  39. 39. Common Discrepancies V.A. CSED
  40. 40. Decision Table – Discrepancies Removed V.A. CSED
  41. 41. Types of Table Entries Limited Entry Form Extended Entry Form Mixed Entry Form ELSE Form V.A. CSED
  42. 42. Decision Table – Limited Entry V.A. CSED
  43. 43. Decision Table – Extended Entry V.A. CSED
  44. 44. Decision Table – Mixed Entry V.A. CSED
  45. 45. Decision Table – Else Form V.A. CSED
  46. 46. Data Dictionary DATA DICTIONARY – Can be defined as a CATALOG or a REPOSITORY of the Elements in a SYSTEM. To Manage details in a Large System. To Document the features of a System. To Communicate a Common Meaning for all System Elements. Record in DD – Data Element, Data Structure. V.A. CSED
  47. 47. Data Dictionary V.A. CSED
  48. 48. Data Dictionary V.A. CSED
  49. 49. Describing Data Elements Data Names Data Description Aliases Length Data Value V.A. CSED
  50. 50. Relation b/w components V.A. CSED
  51. 51. Describing Data Structures Sequence Relationship Selection Relationship Iteration Relationship Optional Relationship V.A. CSED
  52. 52. Sequence Relationship V.A. CSED
  53. 53. Selection Relationship V.A. CSED
  54. 54. Iteration Relationship V.A. CSED
  55. 55. Optional Relationship V.A. CSED
  56. 56. Notation for Structural Rel. in Data V.A. CSED
  57. 57. Data Structure for Student Data V.A. CSED
  58. 58. Data Description & Notation V.A. CSED
  59. 59. Data Flow Name V.A. CSED
  60. 60. Data Structure V.A. CSED
  61. 61. Data Element V.A. CSED
  62. 62. Process V.A. CSED
  63. 63. Structured Analysis Components V.A. CSED
  64. 64. DFD – A Tool for data flow analysis DFD - A Structured, Diagrammatic technique for showing the functions performed by a System & the data flowing Into, out of & within it. Following Data-Oriented Questions about a Target System: What processing is done? What data is Needed? The Context Diagram (Level 0 DFD) is the Highest Level in a Data Flow Diagram and contains only One Process, representing the ENTIRE SYSTEM. V.A. CSED
  65. 65. DFD Style - Yourdon V.A. CSED
  66. 66. DFD Style - Yourdon V.A. CSED
  67. 67. DFD Style - Gane and Sarson V.A. CSED
  68. 68. DFD Style - Gane and Sarson V.A. CSED
  69. 69. Expanding Modules – while locating Thapar University using Google maps – Step 1 V.A. CSED
  70. 70. Expanding Modules – while locating Thapar University using Google maps – Step 2 V.A. CSED
  71. 71. Expanding Modules – while locating Thapar University using Google maps – Step 3 V.A. CSED
  72. 72. Expanding Modules – while locating Thapar University using Google maps – Step 4 V.A. CSED
  73. 73. Expanding Modules – while locating Thapar University using Google maps – Step 5 V.A. CSED
  74. 74. DFD – Expanding Modules V.A. CSED
  75. 75. DFD Principles A System can be decomposed into Subsystems and Subsystems can be decomposed into Lower Level Subsystems and so on. Each Subsystem represents a Process or Activity in which data is processed. At the Lowest Level, Processes can no longer be decomposed. Just as a System must have Input and Output, so a Process must have Input and Output. Data Enters the System from the Environment, Data Flows between Processes within the System and Data is produced as Output from the System. V.A. CSED
  76. 76. Rules for constructing DFD V.A. CSED
  77. 77. DFD Example – A Restaurant V.A. CSED
  78. 78. DFD Example - A Restaurant V.A. CSED
  79. 79. DFD Level 0 (A Restaurant) V.A. CSED
  80. 80. DFD Level 1 (A Restaurant) V.A. CSED
  81. 81. Division of Main Program in Modules V.A. CSED
  82. 82. Example – DFD Construction V.A. CSED
  83. 83. Example – DFD Construction (contd.) V.A. CSED
  84. 84. Presentation Graph V.A. CSED
  85. 85. Physical DFD V.A. CSED
  86. 86. Division in Modules V.A. CSED
  87. 87. Context Diagram (DFD Level -0) V.A. CSED
  88. 88. DFD Level -1 V.A. CSED
  89. 89. Expanding – Invoice Approval (DFD Level -2) V.A. CSED
  90. 90. Expanding - Revise Balance Due (DFD Level -2) V.A. CSED
  91. 91. Expanding - Write Vendor Checks (DFD Level -2) V.A. CSED
  92. 92. Example – Context Diagram V.A. CSED
  93. 93. DFD Level 0 V.A. CSED
  94. 94. Sequence of Logical & Physical View V.A. CSED
  95. 95. Physical & Logical DFD WHAT the System does - Current Physical DFD HOW it does it - Current Logical DFD WHAT it should do - Required Logical DFD HOW it should do it - Required Physical DFD V.A. CSED
  96. 96. 1st Level DFD – Account Payable Processing V.A. CSED
  97. 97. 2nd Level DFD – Invoice Approval Process V.A. CSED
  98. 98. 2nd Level DFD - Maintaining Vendor Balance (A/C Posting) V.A. CSED
  99. 99. 2nd Level DFD – Vendor Payment Processing (Cheque Writing) V.A. CSED
  100. 100. 1st & 2nd Level DFD V.A. CSED
  101. 101. 3rd LEVEL DFD V.A. CSED
  102. 102. Reference List1. System Analysis and Design Methods By Jeffrey L Whitten & Lonnie D Bentley2. Analysis & Design of Information Systems By James A. Senn3. System Analysis & Design By Elias M. Awad4. Modern System Analysis & Design By Jeffrey A. Hoffer, Joey F.George & Joseph S. Valacich5. http://yourdon.com/strucanalysis/wiki/index.php?title=Chapter_96. http://www.ehow.com/about_5095247_definition-data-flow-diagrams.html etc……. V.A. CSED
  103. 103. Thnx… V.A. CSED

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