1. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 1 4/19/2003 Day 3, Part 1 Planning the Schedule

2. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 2 4/19/2003 Outline Basic Concepts in Schedule Planning PERT Charts and Critical Path Analysis GANTT Charts Network Charts Critical Chain Analysis & Slack Management Summary

3. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 3 4/19/2003 The Overall Planning Cycle Analyze Job Manage Risks Execute Generate Detailed Plans Generate Initial Plans Measure, Manage Productivity and Quality

4. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 4 4/19/2003 Estimate Size Estimate Effort and Cost Estimate Schedule Evaluate Source Information Statement of Work Requirements Constraints Standards Processes History etc. WBSSize Effort & Cost Schedule OK Complete Detailed Planning Revise & Negotiate Not OK Detailed Planning - Processes

5. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 5 4/19/2003 Architecture of Spreadsheet Size / Reuse EffortSchedules Cocomo Based Effort Estimate Other Effort Estimates... Analogy based Size Estimate Software Reuse Analysis Final Effort Estimate Productivity Based Effort Estimate Generic Schedule Effort Schedule Other Size Estimates... Final Size Estimate Expert Based Size Estimate

6. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 6 4/19/2003 Basic Concepts in Schedule Planning

7. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 7 4/19/2003 A Hypothetical(?) Scenario I need A detailed schedule! Tell me how long it Will take and when Each task will be Complete. What do I do now? Yes, sir! Right away, Sir.

8. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 8 4/19/2003 Three Levels of Schedule Detail Top Level Schedule –Generally produced during initial planning, based on integrated master schedule for the project, project constraints, deadlines, etc. –Focuses on how software tasks relate to the rest of the project

9. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 9 4/19/2003 Three Levels of Schedule Detail (continued) Generic Schedule (top level software schedule) –Generally produced during effort estimation, based on the process and the information gained from estimating models –The focus is on the major (high level) software tasks and when they occur in time

10. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 10 4/19/2003 Three Levels of Schedule Detail (continued) Detailed Schedule –Generally produced when you are about to execute the project or a phase of the project –The focus is on how and when you will do the detailed work tasks

11. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 11 4/19/2003 Schedules Tend to be Somewhat Flexible You can vary the actual schedule to fit your conditions –You have flexibility in matching the schedule to other project constraints –Cycle time improvement techniques can also improve your schedule –But you can drive up cost as you deviate too far from what is reasonable

12. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 12 4/19/2003 The Optimal Schedule...... depends on people, process, nature of task, environment, etc. … Different models make different assumptions about these factors, reflecting the experience of those who developed the models Until we have a better theoretical foundation, experience remains the best way of predicting your optimal schedule

13. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 13 4/19/2003 Many models use a formula Example: Cocomo formula for optimal schedule: e =.35 for most projects;.38 for easy (organic);.32 for hard (embedded) Effort is measured in staff months Schedule is measured in calendar months Schedule = 2.5 * Effort e Total Time to Do the Job

14. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 14 4/19/2003 The Cocomo Model of Time vs Effort staff- days required to do the work Calendar Time Allocated for the Work Optimal Schedule

15. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 15 4/19/2003 Other Models Vary Grady and Caswell compare five different sources (p34, 35) (see references) Differences stem from: –Type of software being developed –Schedule compression –Organizational differences –Process and methods Hewlett-Packard recommendations: –Measure actual data & keep for the future –Count everything (overtime, etc.)

16. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 16 4/19/2003 For Small Projects... Formulas fit large projects better than small ones And you may not have a good data base of historical schedule information So it may be better to estimate the time in a more detailed manner, as will be shown in the next section and in the course exercises

17. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 17 4/19/2003 Techniques for Developing & Documenting a Detailed Schedule PERT Charts –Show dependencies –Can expand to show resources, timing, and critical path GANTT Charts –Show timing and parallelism Network Charts –Combine the benefits of PERT and GANTT –But you need a tool to manage them

18. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 18 4/19/2003 Steps of Detailed Scheduling 1) Task Dependency and Flow –Shows dependencies, but not timing 2) Task Duration –Shows minimum schedule length –Identifies the critical path 3) Critical Path Analysis –Determines what must change if the schedule is to be reduced

19. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 19 4/19/2003 Steps of Detailed Scheduling 4) Resource Requirements –Shows manpower loading, cash flow, etc. 5) GANTT Chart –Shows relative timing –But not the dependencies 6) Network Chart –Combines GANTT and PERT

20. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 20 4/19/2003 PERT Charts & Critical Path Analysis

21. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 21 4/19/2003 PERT “PERT” stands for “Program Evaluation and Review Technique” or “Performance Estimating & Reporting Tool” (depending on which author you read)

22. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 22 4/19/2003 PERT Origins PERT was developed in the 1940’s as a management tool for complex projects In its fullest form, PERT involves complex statistical analysis of project schedules and plans

23. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 23 4/19/2003 PERT Charts The basic tool of the PERT technique is the PERT Chart, which represents the schedule and resource needs of a project The PERT chart uses the Precedence Diagramming Method (PDM), which is similar to a flow chart, to represent the dependencies among activities

24. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 24 4/19/2003 A Minimal PERT Chart... Lists activities to be performed (from WBS) Indicates dependencies –Activity X must precede activity Y, etc. –This information comes in part from initial planning (life cycle analysis, organizational planning, process definition, etc.)

25. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 25 4/19/2003 Sample PERT Chart from Organizational Planning (in Initial Planning) PrototypeFinal DesignBuildDesign Keyboard CodeDesign Keyboard Software Test Build Keyboard Emulation Delivery Subcontracted SW for Numeric Key Pad Contract This can be produced by hand or with a project management or scheduling tool.

26. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 26 4/19/2003 PrototypeFinal DesignBuildDesign Keyboard CodeDesign Keyboard Software Test Build Keyboard Emulation Delivery Subcontracted SW for Numeric Key Pad Contract An Alternative PERT Notation Touching boxes implies dependency Used to reduce space Used later in this course

27. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 27 4/19/2003 List each task on a “post-it note” or index card Lay out the tasks on a board Indicate task dependencies with lines (arcs) Developing a PERT Chart Step 1 - Task Dependencies Task 1 Task 3 Task 6Task 7 Task 8 Task 2Task 5 Task 4 Task 9

28. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 28 4/19/2003 Design Test Code Design Spec Integrate Develop Hardware Code VerifyTest Evaluating Dependencies

29. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 29 4/19/2003 “Test” Task depends on “Code” and “Test Code” Design Test Code Design Spec Integrate Develop Hardware Code VerifyTest Identifying Dependencies What depends on what?

30. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 30 4/19/2003 Design Test Code Design Spec Integrate Develop Hardware Code VerifyTest Who needs this? (no successor) Identifying Dependencies What dependencies are unknown?

31. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 31 4/19/2003 Design Test Code Design Spec Integrate Develop Hardware Code VerifyTest External task that we depend on Identifying Dependencies What external tasks do we depend on?

32. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 32 4/19/2003 Types of PERT Dependencies Finish to Start First task must finish before the second starts Start to Start Second task must start x months after first starts Finish to Finish Second task must finish y months after first finishes x y Task 5 Task 2 3 7 6 Task 1Task 3Task 6Task 7 Task 8 Task 4 Task 9

33. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 33 4/19/2003 With most PERT tools, you can specify a priority among parallel tasks With most PERT tools, you can specify a priority among parallel tasks Task 1 Task 3 Task 5 Task 2 Task 4 Task 5 Task 1 Task 3 Task 2 Task 4 Verifying Dependencies Do not overconstrain -- use only the the essential dependencies The second PERT chart represents a much more flexible plan

34. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 34 4/19/2003 What to Learn from a Basic PERT Chart Identify dependencies you did not know existed Identify missing dependencies where you do not know the successor or the predecessor Identify critical dependencies, such as a hardware activity that will hold you up if it is late

35. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 35 4/19/2003 NOTE PERT Charts are a good method for developing a detailed process description as well as developing a project schedule PrototypeFinal DesignBuildDesign Keyboard CodeDesign Keyboard Software Test Build Keyboard Emulation Delivery Subcontracted SW for Numeric Key Pad Contract

36. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 36 4/19/2003 Steps of PERT Scheduling 1) Basic PERT -- task dependency and flow –shows dependencies, but not timing 2) More Complete PERT -- task duration –shows minimum schedule length 3) Critical path –shows what tasks contribute to minimum schedule length (what tasks need to be shortened to shorten the overall schedule) 4) Full PERT - resource requirements –shows manpower loading, resource needs, etc. 

37. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 37 4/19/2003 Developing a PERT Chart Step 2 - Task Duration Lay out a time line at the bottom of the board For each task, estimate its duration and write that information on the post-it note. –Can be minimum feasible duration or expected duration based on availability of resources Place each task in its appropriate position relative to the time line

38. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 38 4/19/2003 Developing a PERT Chart Step 2 - Task Duration (continued) Proper placement shows earliest start date for each task [or latest start date] 20 weeks 8 weeks Minimum total time for whole activity is 26 weeks JFMAMJJASOND 6 weeks 8 weeks 12 weeks 26 weeks

39. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 39 4/19/2003 What to Learn After Durations are Added The first task to focus on is the very last task –Will it complete by the project deadline? If not, how can you make the whole schedule shorter? The answer starts with determining the Critical Path

40. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 40 4/19/2003 The Critical Path is... … the longest calendar path through the schedule from the first to the last activity Task A Task C Task B Task D Task E The Critical Path in the above example is A,C,D

41. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 41 4/19/2003 The Critical Path is... … the path that must be shortened in order to shorten the whole schedule … the path that drives schedule slips –If a critical path task slips, the whole schedule slips … the riskiest part of the schedule Be especially wary when the critical path involves dependency on external tasks that you do not control!

42. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 42 4/19/2003 If the schedule is small, “eyeball” and determine which path is the longest. Otherwise a tool can be used Critical Path => min possible schedule 6 weeks 3 weeks 5 weeks Critical Path Tasks Non-Critical Path Tasks Developing a PERT Chart Step 3 - Analyzing the Critical Path

43. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 43 4/19/2003 What if the Minimum Schedule is Too Long? You must find a way to cut the schedule Begin with tasks on the critical path –Try to divide them into smaller tasks that can be done simultaneously –Assign more resources - do them faster –Cut functionality or defer until later Note that when you do this you might create a different critical path

44. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 44 4/19/2003 Developing a PERT Chart Step 4 - Resource Requirements Determine the resource requirements of each task: –Equipment, facilities, etc. –Key personnel –Total labor effort (staff days, etc) –May also show minimum and maximum reasonable allocations, i.e., 8 staff weeks: minimum 2 weeks (4 people) maximum 8 weeks (1 person)

45. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 45 4/19/2003 Resources Write this information on the index card or post-it-note Vary labor totals or types of personnel assigned to different tasks in order to meet schedule needs 8 staff weeks: 2 weeks, 4 people 8 staff weeks: 4 weeks, 2 people 8 staff weeks: 2 weeks, 3 senior people These options may reduce the critical path or even remove this task from the critical path These options may reduce the critical path or even remove this task from the critical path

46. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 46 4/19/2003 Scheduling Tools can... … find critical path/shortest schedule … find minimum and total effort levels … do simulation of schedule to determine likely outcomes when exact duration are indefinite … assist in “what if” analysis of possible alternatives … revise schedules with minimal effort  Sample tools: Microsoft Project®, Primavera®

47. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 47 4/19/2003 “Schedule from the back” concept Minimal execution times for each task Assuming adequate staff, task E must be started at least 7 weeks before final integration, whereas task A must be started at least 11 weeks before! Using PERT Charts to Decide on Development Sequence Final Integration 4 weeks C 1 week D 3 weeks F 4 weeks E 2 weeks B 6 weeks A 2 weeks

48. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 48 4/19/2003 Shopload Shows Resource Needs and Allocation by Time Period

49. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 49 4/19/2003 Suggested Notation for Post-it Notes Yellow –Normal Tasks Pink or Red –External Tasks that You Depend On Blue –External Tasks that Depend on You

50. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 50 4/19/2003 Schedule for Project P (sample) JFMAMJJASOND

51. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 51 4/19/2003 Gizmo hardware must arrive by June 1 –We must watch their schedule Joe and Mary must be available 100% for this project Integration must wait until Sept 15 Programmers must all be available to start on March 1 At least three test sets must be available during the month of August Gizmo hardware must arrive by June 1 –We must watch their schedule Joe and Mary must be available 100% for this project Integration must wait until Sept 15 Programmers must all be available to start on March 1 At least three test sets must be available during the month of August Critical Dependencies, Issues, Assumptions, and Lessons Learned (sample)

52. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 52 4/19/2003 Steps of Detailed Scheduling 1) Task Dependency and Flow –Shows dependencies, but not timing 2) Task Duration –Shows minimum schedule length –Identifies the critical path 3) Critical Path Analysis –Determines what must change if the schedule is to be reduced   

53. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 53 4/19/2003 Steps of Detailed Scheduling 4) Resource Requirements –Shows manpower loading, cash flow, etc. 5) GANTT Chart –Shows relative timing –But not the dependencies 6) Network Chart –Combines GANTT and PERT 

54. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 54 4/19/2003 GANTT Charts These are devised from the same data used in a PERT chart, but show the relative time phasing of the tasks instead of the dependencies Each “activity” box is sized to be proportional to the length of time it takes The boxes are lined up, usually in the order of execution, to show what is happening at what time

55. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 55 4/19/2003 Sample Gantt Chart Vertical line represents current date Task 2 Task 3 Task 6 Task 5 Task 1 Task 7 Task 4

56. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 56 4/19/2003 Task 6 Task 5 Task 7 Does Task 6 depend on Task 5? Can Task 5 finish on time? Gantt Chart does NOT tell you... … task dependencies … significance or impact of schedule slips … whether it is realistic to expect you to meet the schedule … critical path

57. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 57 4/19/2003 Network Charts

58. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 58 4/19/2003 JanFebMarAprMayJunJulAug Network Chart -- Combining the Pert and Gantt Horizontal width indicates schedule length Arcs indicate dependencies Horizontal position indicates scheduled time and task parallelism Task A Task C Task B Task D Task E

59. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 59 4/19/2003 Network Chart Summary Tells you the duration of tasks and their interdependencies. Shows Critical Path Can be color coded to show different parts of the project –Software in blue, mechanical in red, etc. But it still cannot tell you if the schedule is realistic

60. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 60 4/19/2003 Project Management and Scheduling Tools Most such tools can show a PERT or GANTT chart More capable tools will show a network chart, which is hard to do by hand But tools take a lot of work to enter data and the data changes a lot in the early steps of detailed scheduling

61. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 61 4/19/2003 Recommendations Regarding Management/Scheduling Tools Do a PERT chart by hand and work through the fundamental relationships Then use a tool after things have settled down Select a tool carefully –Some cannot handle the complexity of a very large project –But the most capable tools are harder to use

62. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 62 4/19/2003 Using Network or Pert Charts to Establish a Schedule Earliest Completion Date –Tells you how soon you can complete –Tells you the earliest you can start each task Latest Start Date –Tells you how late you can start and still meet the deadline –Tells you the latest you can start each task Critical Chain Analysis –Adds analysis of critical resource needs –Can help you manage to meet short cycle time

63. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 63 4/19/2003 Earliest Completion Date A, C, E, F can slip without hurting schedule E 4 weeks Final Integration 4 weeks G 3 weeks D 6 weeks A 3 weeks B 4 weeks C 2 weeks F 2 wks 17 weeks min. Earliest Start Date Later Start Date

64. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 64 4/19/2003 Latest Start Date A, C, E, F can start late without hurting schedule B, D, G, Final must start as shown, since on critical path A, C, E, F can start late without hurting schedule B, D, G, Final must start as shown, since on critical path Final Integration 4 weeks G 3 weeks D 6 weeks A 2 weeks B 4 weeks C 2 weeks F 2 wk E 4 weeks 17 weeks min. Earlier Start Date Latest Start Date

65. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 65 4/19/2003 Critical Chain Analysis & Slack Management

66. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 66 4/19/2003 A Critical Resource is a resource that is required on each of two or more tasks –A piece of equipment –An individual with unique skills If shared, each task gets only part time use ? You are essential to my project My project will fail without you Critical Resources

67. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 67 4/19/2003 If two tasks need a resource, one must give it up or both must run slower But it is tempting to fantasize that you can share resources without such high waste Sharing a Resource Means Less Efficiency Percent UseAvailabilityWaste 100%85%15% 50%+50%40%+40%20% 33%+33%+33%25%+25%+25%25% 25%+....17.5%+....30%

68. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 68 4/19/2003 Using Critical Resources If the resource is critical, it is also known as a constraint The fundamental rule of constraint management is that you should maximize the efficiency of the constraint Which means you avoid overusing constraints and wasting time on inefficient sharing

69. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 69 4/19/2003 If Task B needs a resource that is also needed by Task A then Task B is on the Critical Chain The Critical Chain The critical chain consists of all tasks using resources that are needed on the critical path Task A Task C Task B Task D Task E

70. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 70 4/19/2003 Critical Chain Analysis Start with Latest Start Date schedule Mark critical path tasks as “on the critical chain” & identify resources needed for these tasks If also needed elsewhere in parallel tasks, mark those tasks as “critical chain” tasks Reschedule those tasks earlier, so there is no conflict of resources This may change the critical path!

71. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 71 4/19/2003 Conventions for Critical Chain Analysis Conflict Earlier Start Date Latest possible Start Date Normal Tasks Critical Path and Critical Chain but Not Critical Path Critical Path Tasks

72. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 72 4/19/2003 Example of Critical Chain Analysis G and F need the same critical resource So F and its predecessors (E, C) must be started sooner G and F need the same critical resource So F and its predecessors (E, C) must be started sooner A 3 weeks Final Integration 4 weeks G 3 weeks D 6 weeks B 4 weeks E 4 weeks C 2 weeks F 2 wk 17 weeks min.

73. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 73 4/19/2003 A Further Example A and C cannot proceed in parallel This changes the critical path and lengthens the schedule! A and C cannot proceed in parallel This changes the critical path and lengthens the schedule! H 4 wks G 3 wks A 3 wks E 4 wks C 2 wks F 2 wks B 4 wks D 6 wks 18 weeks minimum Suppose A and C need the Same Critical Resource

74. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 74 4/19/2003 Other Schedule Management Techniques Do more careful monitoring of critical path and critical chain tasks Start critical chain tasks as soon as you can - to provide maximum risk control DO NOT allow people to include slack time in their task schedules. All slack should be held in reserve by a higher level manager

75. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 75 4/19/2003 Example of Slack Management Problem Final Integration 4 weeks G 3 weeks E 4 weeks C 2 weeks Final Integration 4 weeks G 3 weeks E 4 weeks C 2 weeks Plan: C and E allow slack to reduce risk Actual: C and E wait until last possible minute to start

76. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 76 4/19/2003 What Might Really Happen Final Integration 4 weeks G 5 weeks E 4 weeks C 2.5 weeks Reality: C and G slip a little bit … C’s slip is absorbed by E’s slack But G’s slip causes the whole project to slip 2 weeks C’s slip is absorbed by E’s slack But G’s slip causes the whole project to slip 2 weeks

77. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 77 4/19/2003 Slack Management Final Integration 4 weeks G 5 weeks E 4 weeks C 2.5 weeks Actual - Slack can be applied to any task that slips, so the project stays on schedule Final Integration 4 weeks G 3 weeks E 4 weeks C 2 weeks Plan: C and E have no slack Slack - 4 wks

78. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 78 4/19/2003 Critical path analysis identifies what tasks must be shortened to shorten the overall schedule Adding resource requirements enables you to decide on sequencing and when to schedule tasks and resources GANTT shows relative timing but not dependencies, flow Network chart shows both, but requires a more capable tool Summary Schedule Estimation & Planning

79. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 79 4/19/2003 Critical Chain shows resource conflicts between critical path tasks & other tasks Critical Resources must be managed to avoid impact on critical path Critical Chain Analysis shows which tasks must be started earlier in order to avoid resource conflicts Slack Management gives maximum risk control and shortest cycle time Summary Schedule Estimation & Planning

80. Copyright © 1995-2003, Dennis J. Frailey, All Rights Reserved Day 3, Part 1, Page 80 4/19/2003 1) Brassard, Michael, The Memory Jogger Plus+, Goal/QPC, Methuen MA, 1989. 2) Goldratt, Eliyahu M. & Jeff Cox, The Goal, (North River Press, 1984.) Also Theory of Constraints and It’s Not Luck. 3) Thayer, Richard H., ed., Software Engineering Project Management, IEEE Computer Society Press, 1994. 4) U. of West Florida, PERT Home page, http://www.uwf.edu/~coehelp/studentaccounts/rnew /perthome.html References Schedule Estimation & Planning