Appraise System Building

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Appraise System Building

  1. 1. 12.1 12. APPROACHES TO SYSTEMS-BUILDING
  2. 2. <ul><li>APPRAISE SYSTEM BUILDING ALTERNATIVES </li></ul><ul><li>COMPARE STRENGTHS, WEAKNESSES OF APPROACHES </li></ul><ul><li>ASSESS SOLUTIONS TO PROBLEMS CREATED BY APPROACHES </li></ul><ul><li>DESCRIBE TOOLS, METHODOLOGIES OF SYSTEMS DEVELOPMENT </li></ul><ul><li>* </li></ul>LEARNING OBJECTIVES 12.2
  3. 3. MANAGEMENT CHALLENGES <ul><li>TRADITIONAL SYSTEMS LIFECYCLE </li></ul><ul><li>ALTERNATIVE SYSTEM-BUILDING APPROACHES </li></ul><ul><li>SYSTEM-BUILDING METHODOLOGIES & TOOLS </li></ul><ul><li>* </li></ul>12.3
  4. 4. SYSTEM LIFECYCLE <ul><li>PROJECT DEFINITION: Is there a problem? Can it be solved with a project? </li></ul><ul><li>SYSTEM STUDY: Analyze problems in existing systems; define objectives evaluate alternatives </li></ul><ul><li>DESIGN: Logical & physical specifications for systems solution </li></ul><ul><li>PROGRAMMING: Develop software code </li></ul><ul><li>* </li></ul>12.4
  5. 5. SYSTEM LIFECYCLE <ul><li>INSTALLATION: Construct, test, train, convert to new system </li></ul><ul><li>POSTINSTALLATION: On-going evaluation, modifications for improvement to meet new requirements </li></ul><ul><li>NECESSARY FOR LARGE, COMPLEX SYSTEMS & PROJECTS </li></ul><ul><li>* </li></ul>12.5
  6. 6. SYSTEM LIFECYCLE <ul><li>CAN BE COSTLY, TIME CONSUMING </li></ul><ul><li>MAY ENCOURAGE FREEZING SPECIFICATIONS EARLY IN DEVELOPMENT </li></ul><ul><li>MAY NOT BE SUITABLE FOR SMALL, LESS STRUCTURED SYSTEMS </li></ul><ul><li>* </li></ul>12.6
  7. 7. ALTERNATIVE SYSTEM-BUILDING APPROACHES <ul><li>PROTOTYPING </li></ul><ul><li>APPLICATION SOFTWARE PACKAGES </li></ul><ul><li>END-USER DEVELOPMENT </li></ul><ul><li>OUTSOURCING </li></ul><ul><li>* </li></ul>12.7
  8. 8. PROTOTYPING <ul><li>PROCESS OF BUILDING EXPERIMENTAL SYSTEM TO DEMONSTRATE, EVALUATE APPROACH; USERS REFINE NEEDS </li></ul><ul><li>PROTOTYPE: Preliminary working version of information system for demonstration, evaluation purposes </li></ul><ul><li>ITERATIVE PROCESS </li></ul><ul><li>* </li></ul>12.8
  9. 9. STEPS IN PROTOTYPING <ul><li>1. IDENTIFY USER’S REQUIREMENTS </li></ul><ul><li>2, DEVELOP PROTOTYPE </li></ul><ul><li>3, USE PROTOTYPE </li></ul><ul><li>4. REVISE & ENHANCE PROTOTYPE </li></ul><ul><li>BEST FOR DESIGN OF END-USER INTERFACE: How end-user interacts with system </li></ul><ul><li>* </li></ul>12.9
  10. 10. APPLICATION SOFTWARE PACKAGES <ul><li>PREWRITTEN, PRECODED APPLICATION SOFTWARE, COMMERCIALLY AVAILABLE FOR SALE OR LEASE </li></ul><ul><li>GEARED TO COMMON REQUIREMENTS </li></ul><ul><li>CUSTOMIZATION: Modification of software to meet organization’s needs </li></ul><ul><li>MUST WEIGH COSTS / BENEFITS </li></ul><ul><li>* </li></ul>12.10
  11. 11. SELECTED EXAMPLES OF APPLICATION PROGRAMS <ul><li>ACCOUNTS RECEIVABLE; BOND & STOCK MANAGEMENT; COMPUTER-AIDED DESIGN (CAD) ; DOCUMENT IMAGING; E- MAIL; ENTERPRISE . RESOURCE PLANNING (ERP); GROUPWARE; HEALTH CARE; HOTEL . MANAGEMENT; INTERNET TELEPHONE; INVENTORY CONTROL; JOB COSTING; LIBRARY SYSTEMS; LIFE INSURANCE; MAILING LABELS; MATHEMATICAL / STATISTICAL MODELING; ORDER PROCESSING; PAYROLL; PROCESS CONTROL; TAX ACCOUNTING; WEB BROWSER; WORD PROCESSING </li></ul><ul><li>* </li></ul>12.11
  12. 12. CUSTOMIZATION <ul><li>MODIFYING SOFTWARE PACKAGE </li></ul><ul><li>TO MEET ORGANIZATION’S UNIQUE REQUIREMENTS </li></ul><ul><li>WITHOUT DESTROYING INTEGRITY OF PACKAGE </li></ul><ul><li>RAISES DEVELOPMENT COSTS </li></ul><ul><li>* </li></ul>12.12
  13. 13. EFFECTS OF CUSTOMIZING SOFTWARE ON TOTAL IMPLEMENTATION COSTS 12.13 0 2 4 6 8 10 0.5 1 2 3 4 5 % LINES OF CODE CONVERTED TOTAL IMPLEMENTATION COSTS
  14. 14. <ul><li>DESCRIPTION (PRESENT, PROPOSED) </li></ul><ul><li>RELIABILITY </li></ul><ul><li>BACKUP </li></ul><ul><li>SERVICES </li></ul><ul><li>SYSTEM SPECIFICATIONS </li></ul><ul><li>CRITERIA </li></ul><ul><li>DEMONSTRATION (PROTOTYPE) </li></ul><ul><li>SCHEDULE (BENCH MARKS) </li></ul><ul><li>PRICE (PENALTIES) </li></ul><ul><li>SPECIFIC QUESTIONS </li></ul><ul><li>PROCEDURES FOR RESPONSE </li></ul><ul><li>* </li></ul>REQUEST FOR PROPOSAL (RFP ) Source: Senn, Information Technology in Business (1995) 12.14
  15. 15. END-USER DEVELOPMENT <ul><li>END-USERS DEVELOP INFORMATION SYSTEM </li></ul><ul><li>WITH LITTLE HELP FROM </li></ul><ul><li>TECHNICAL SPECIALISTS </li></ul><ul><li>USING 4th GENERATION TOOLS </li></ul><ul><li>* </li></ul>12.15
  16. 16. END-USER DEVELOPMENT <ul><li>STRENGTHS: </li></ul><ul><li>IMPROVED REQUIREMENTS DETERMINATION </li></ul><ul><li>INCREASED USER INVOLVEMENT & SATISFACTION </li></ul><ul><li>REDUCED APPLICATION BACKLOG </li></ul><ul><li>* </li></ul>12.16
  17. 17. END-USER DEVELOPMENT <ul><li>WEAKNESSES: </li></ul><ul><li>RELATIVELY INEFFICIENT </li></ul><ul><li>SLOW TRANSACTION PROCESSING </li></ul><ul><li>MAY CARRY HIGH COST </li></ul><ul><li>LARGE FILES CAN DEGRADE PERFORMANCE </li></ul><ul><li>NONPROCEDURAL APPROACH MAY HAMPER LOGIC & UPDATING REQUIREMENTS </li></ul><ul><li>* </li></ul>12.17
  18. 18. MANAGING END-USER DEVELOPMENT <ul><li>INFORMATION CENTER: </li></ul><ul><li>SPECIAL FACILITY WITHIN ORGANIZATION </li></ul><ul><li>PROVIDES TRAINING, SUPPORT FOR END-USER-COMPUTING </li></ul><ul><li>* </li></ul>12.18
  19. 19. OUTSOURCING <ul><li>CONTRACTING: </li></ul><ul><li>COMPUTER CENTER OPERATIONS </li></ul><ul><li>TELECOMMUNICATIONS NETWORKS </li></ul><ul><li>APPLICATION DEVELOPMENT </li></ul><ul><li>TO EXTERNAL VENDORS </li></ul><ul><li>* </li></ul>12.19
  20. 20. OUTSOURCING <ul><li>WHEN TO OUTSOURCE: </li></ul><ul><li>IF FIRM WON’T DISTINGUISH ITSELF BY DEVELOPING APPLICATION </li></ul><ul><li>PREDICTABILITY OF UNINTERRUPTED SERVICE NOT IMPORTANT </li></ul><ul><li>IF EXISTING SYSTEM IS LIMITED, INEFFECTIVE, INFERIOR </li></ul><ul><li>* </li></ul>12.20
  21. 21. SYSTEM BUILDING METHODOLOGIES <ul><li>STRUCTURED METHODOLOGIES </li></ul><ul><li>OBJECT- ORIENTED SOFTWARE DEVELOPMENT </li></ul><ul><li>COMPUTER AIDED SOFTWARE ENGINEERING (CASE) </li></ul><ul><li>SOFTWARE REENGINEERING </li></ul><ul><li>* </li></ul>12.21
  22. 22. STRUCTURED METHODOLOGIES <ul><li>TOP DOWN, STEP BY STEP, EACH STEP BUILDS ON PREVIOUS </li></ul><ul><li>STRUCTURED ANALYSIS </li></ul><ul><li>STRUCTURED DESIGN </li></ul><ul><li>STRUCTURED PROGRAMMING </li></ul><ul><li>FLOWCHARTS </li></ul><ul><li>* </li></ul>12.22
  23. 23. STRUCTURED ANALYSIS <ul><li>DEFINES SYSTEM INPUTS, PROCESSES, OUTPUTS </li></ul><ul><li>PARTITIONS SYSTEM INTO SUBSYSTEMS OR MODULES </li></ul><ul><li>LOGICAL, GRAPHICAL MODEL OF INFORMATION FLOW </li></ul><ul><li>DATA FLOW DIAGRAM: Graphical display of component processes, flow of data </li></ul><ul><li>* </li></ul>12.23
  24. 24. SYMBOLS FOR DATA FLOW DIAGRAMS (DFD): DATA FLOW PROCESS SOURCE OR SINK FILE 12.24
  25. 25. DATA FLOW DIAGRAM: 12.25  GENERATE BILL CUSTOMER GENERATE BALANCE GENERATE REPORT MANAGER PAYMENT FILE CUSTOMER FILE
  26. 26. STRUCTURED ANALYSIS <ul><li>DATA DICTIONARY: Controlled definitions of descriptions of all data, such as variable names & types of data </li></ul><ul><li>PROCESS SPECIFICATIONS: Describes logic of processes at module level </li></ul><ul><li>* </li></ul>12.26
  27. 27. STRUCTURED DESIGN <ul><li>DESIGN RULES / TECHNIQUES TO DESIGN SYSTEM, TOP DOWN IN HIERARCHICAL FASHION </li></ul><ul><li>STRUCTURE CHART </li></ul><ul><li>STRUCTURED PROGRAMMING </li></ul><ul><li>MODULE </li></ul><ul><li>SEQUENCE CONSTRUCT </li></ul><ul><li>SELECTION CONSTRUCT </li></ul><ul><li>* </li></ul>12.27
  28. 28. 12.28 CALCULATE GROSS PAY CALCULATE NET PAY CALCULATE PAY PROCESS PAYROLL UPDATE MASTER FILE GET VALID INPUTS WRITE OUTPUTS GET INPUTS VALIDATE INPUTS WRITE OUTPUTS HIGH LEVEL STRUCTURE CHART: HIGH LEVEL STRUCTURE CHART: (WHITE BOXES ARE MODULES) (WHITE BOXES ARE MODULES )
  29. 29. STRUCTURED PROGRAMMING: <ul><li>DISCIPLINE TO ORGANIZE, CODE PROGRAMS </li></ul><ul><li>SIMPLIFIES CONTROL PATHS </li></ul><ul><li>EASY TO UNDERSTAND, MODIFY </li></ul><ul><li>MODULE HAS ONE INPUT, ONE OUTPUT </li></ul><ul><li>* </li></ul>12.29
  30. 30. STRUCTURED PROGRAMMING: <ul><li>MODULE: Logical unit of program. performs specific task(s) </li></ul><ul><li>SEQUENCE CONSTRUCT: Sequential steps or actions in program logic; streamlines flow </li></ul><ul><li>SELECTION CONSTRUCT: IF Condition R is True THEN Action C ELSE Action D </li></ul><ul><li>ITERATION CONSTRUCT: WHILE Condition is True DO Action E </li></ul><ul><li>* </li></ul>12.30
  31. 31. SYSTEM FLOWCHART SYMBOLS: 12.31
  32. 32. SYSTEM FLOWCHART: 12.32 LOAD & VALIDATE COMPARE & UPDATE VALID TRANS- ACTIONS PAYROLL SYSTEM TIME CARDS HUMAN RESOURCES DATA PAYROLL MASTER UPDATED PAYROLL MASTER DIRECT DEPOSITS GENERAL LEDGER PAYROLL REPORTS & CHECKS PAYROLL MASTER
  33. 33. PROGRAM FLOWCHART SYMBOLS: 12.33
  34. 34. PROGRAM FLOWCHART: 12.34 PROCESS A PROCESS B SEQUENCE PROCESS C PROCESS D R TRUE SELECTION PROCESS E S TRUE ITERATION
  35. 35. PROGRAM FLOWCHART: 12.35 1 END REPORT MORE? 2 PRINT 1 2 START READ >$10,000 <$10,000 PROCESS A PROCESS B
  36. 36. OBJECT - ORIENTED SOFTWARE DEVELOPMENT <ul><li>DE-EMPHASIZES PROCEDURES </li></ul><ul><li>SHIFTS FOCUS FROM MODELS & DATA </li></ul><ul><li>TO OBJECTS , WHICH COMBINE DATA & PROCEDURES </li></ul><ul><li>OBJECTS REUSABLE </li></ul><ul><li>SYSTEM: Classes; objects; relationships </li></ul><ul><li>REDUCES DEVELOPMENT TIME & COST </li></ul><ul><li>* </li></ul>12.36
  37. 37. COMPUTER AIDED SOFTWARE ENGINEERING (CASE) <ul><li>AUTOMATION OF SOFTWARE METHODOLOGIES </li></ul><ul><li>PRODUCES CHARTS; DIAGRAMS; SCREEN & REPORT GENERATORS; DATA DICTIONARIES; PROGRESS REPORTS; ANALYSIS; CHECKING TOOLS; CODE; DOCUMENTATION </li></ul><ul><li>* </li></ul>CASE 12.37
  38. 38. COMPUTER AIDED SOFTWARE ENGINEERING (CASE) <ul><li>INCREASES PRODUCTIVITY & QUALITY: </li></ul><ul><li>ENFORCES DEVELOPMENT DISCIPLINE </li></ul><ul><li>IMPROVES COMMUNICATION </li></ul><ul><li>DESIGN REPOSITORY FOR OBJECTS </li></ul><ul><li>AUTOMATES TEDIOUS TASKS </li></ul><ul><li>AUTOMATES TESTING & CONTROL </li></ul><ul><li>REQUIRES ORGANIZATIONAL DISCIPLINE </li></ul><ul><li>* </li></ul>CASE 12.38
  39. 39. SOFTWARE REENGINEERING <ul><li>SALVAGES & UPGRADES AGING SOFTWARE </li></ul><ul><li>DELAYS EXPENSIVE REPLACEMENT </li></ul><ul><li>REVERSE ENGINEERING: CONVERTING EXISTING PROGRAMS, FILES, DATABASE FOR USE IN NEW APPLICATIONS </li></ul><ul><li>* </li></ul>12.39
  40. 40. SOFTWARE REENGINEERING <ul><li>REVISE DESIGN & PROGRAM SPECIFICATIONS </li></ul><ul><li>FORWARD ENGINEERING: USE REVISED MATERIALS TO GENERATE NEW, STRUCTURED CODE; STRUCTURED & MAINTAINABLE SYSTEM </li></ul><ul><li>* </li></ul>12.40
  41. 41. Connect to the INTERNET PRESS LEFT MOUSE BUTTON ON ICON TO CONNECT TO THE LAUDON & LAUDON WEB SITE FOR MORE INFORMATION ON THIS CHAPTER 12.41
  42. 42. 12.42 12. APPROACHES TO SYSTEMS-BUILDING

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