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Unit 10 – Network Logic and Scheduling

Unit 10 – Network Logic and Scheduling. Sectional slide. Agenda. Unit 10: Network Logic and Scheduling Objectives A practical approach to project scheduling Schedule types Project scheduling Network analysis Leveling Rolling-wave planning concept Gantt chart Milestone chart

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Unit 10 – Network Logic and Scheduling

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  1. Unit 10 – Network Logic and Scheduling Sectional slide

  2. Agenda Unit 10: Network Logic and Scheduling • Objectives • A practical approach to project scheduling • Schedule types • Project scheduling • Network analysis • Leveling • Rolling-wave planning concept • Gantt chart • Milestone chart • Key Messages - Unit 10

  3. Objectives At the end of this module, you will be able to - • Define networks and schedules • Identify various types of logic networks and approaches, and weigh their relative merits for specific development projects • Use logic networks and scheduling approaches appropriate to their particular projects • Integrate a WBS into a logic network and determine a schedule for that network • Incorporate risk into scheduling considerations

  4. A Practical Approach to Project Scheduling Working rules • Time is usually the critical factor • Scheduling and risk management functions are the foundation for project control • You should be able to predict probable delays, initiate steps, and always include in a report - • Impact of the delay • Steps to be taken to avoid or reduce delay • "Key events" (to be defined) and milestones are to be recognized as deadlines • Anyone who is not fulfilling his or her timely obligation should be immediately notified The project manager is not a "schedule mechanic"

  5. A Practical Approach to Project Scheduling (continued) The tools • Use a project management tool (like MS Project) for scheduling based on the common WBS • Have internal and external suppliers, project team members, and business partners participate in the scheduling (according to the main project schedule), identify who is allocated to a task, and report on agreed-upon key events • Make obligations such as submitting data, approving deliverables, and meeting other obligations, an integrated part of the project schedule • Emphasize key events more than activities • Strictly define events regarding contents so that cause of a delay can be concisely and quickly identified Project management is management of interfaces!

  6. Schedule Types • Networking • Activity-on-arrow (AOA) • Precedence diagram method (PDM) • Gantt chart • Milestone chart

  7. Project Scheduling

  8. Network Scheduling • Schedule flows from WBS work packages' planned or actual duration • Schedules may be driven by amount of resources required • Schedule is a major element of project baseline (along with expense and technical considerations) • Shows time to finish and activity interdependencies • Provides greatest amount of information - useful for detailed analysis • Two types • Activity-on-arrow • Precedence diagram method

  9. Essential Scheduling Data (Example) Activities and Times

  10. Networks can be used for CPM and Slack Analysis

  11. Precedence Diagram Method

  12. Basic Scheduling Terminology • Activity: A task (work package) performed over a period of time; a specific piece of defined work from WBS • Milestone: Zero time duration activity • Relationships: Dependencies that exist between activities • Free float: The amount of time an activity can be delayed without delaying the early start of any immediately following activities

  13. Basic Scheduling Terminology (continued) • Total float: The amount of time that an activity may be delayed from its early start without delaying the project finish date • Critical path: Longest time period from start to completion of a project; also the shortest total length of the project • Lag: Imposed delay between the start or finish of one activity and the start or finish of another

  14. Basic Scheduling

  15. Types of Relationships Activity 1 must be totally finished before Activity 2 can start: traditional Example: Define requirements (Activity 1), perform DCUT - design, code, unit test (Activity 2)

  16. Types of Relationships (continued) Activity 2 cannot finish until Activity 1 finishes Example: Activity 2 (reviewing the high-level design) cannot be finished until Activity 1 (writing the high-level design) is finished

  17. Types of Relationships (continued) Activity 2 cannot start until Activity 1 begins; a lag of n time units can be defined Example: Reviewing the specifications (Activity 2) can begin after writing the specifications (Activity 1) begins

  18. Hard Coding Relationship Constraints • Start no earlier than (SNET) • Start no later than (SNLT) • Finish no earlier than (FNET) • Finish no later than (FNLT) • Must start on (MSO) • Must finish on (MFO)

  19. Using the Hard Constraints Cautions • They will override the normal critical-path calculations • They remove naturally occurring float in your schedule Useful for - • Creating milestone charts • Positioning activities to eliminate excessive float

  20. Network Calculations • Forward pass through the network (beginning at project start) determines Early Start and Early Finish for each activity • Backward pass through the network (beginning at project finish) determines Late Finish and Late Start for each activity

  21. Forward Pass • Established: Project Start date • Project Start date is the Early Start date for first network activity • Work from left to right, top to bottom of the network • When an activity has multiple predecessors (P), select highest Early Finish date as Early Start date of successor (S) • Calculations • ESP + Duration = EFP • EFP + Lag = ESS

  22. Forward Pass (continued) Full precedence diagram

  23. Backward Pass • Established: Project Finish date (from last activity in Forward Pass) • Project Finish date is the Late Finish date for last network activity in the Backward Pass • Work from left to right, top to bottom of network • When a predecessors (P) has multiple successors (S), select the lowest Late Start date as the Late Finish of the predecessor • Calculations • LFS - Duration = LSS • LSS - Lag = LFP

  24. Backward Pass (continued) Full precedence diagram

  25. Float/Slack • Float = Late Finish - Early Finish or • Float = Late Start - Early Start • Float/Slack > 0 (time is available) • Float/Slack = 0 (path is critical) • Float/Slack < 0 (project is behind schedule/critically late)

  26. Critical Path • Longest of all paths through the project • Shortest time to complete the project • Path with least float/slack time

  27. Process for Computing Critical Path Network Schedule Step 1 Establish a "begin" activity Step 2 Identify all activities that can begin immediately (that is, that have no predecessors) Step 3 Identify what, as a result of the activities being started/completed, can now start/end Step 4 Complete process until all predecessors and successors have been identified Step 5 Make "end" the final activity Step 6 Calculate the forward pass; when multiple dates must be passed forward, select the latest date Step 7 Establish the natural end date of the project Step 8 Calculate the backward pass; when multiple dates must be passed backward, select the earliest date Step 9 Calculate float Step 10 Identify the critical path and paths with low levels of float Step 11 Restrict the project by adding any intermediate end date constraints Step 12 Recalculate the backward pass Step 13 Recalculate float Step 14 Identify the critical path and paths with low levels of float Step 15 Use networking techniques to eliminate any negative float

  28. Benefits of Critical Path Method • Shows explicit relationships • Coordinates "big picture" • Lays out flow of work • Encourages careful task analysis

  29. Exercise: Precedence Diagram Method 12 14 8 FS+6 B D G 12 8 14 A H I 16 13 C E 19 SS+10 F Calculate the forward and backward passes Identify the critical path Calculate the float for each path

  30. Network Analysis • Is the critical path what I expected? • How much float is in the schedule? • Do I need to do anything about it? • Should activities with large amounts of float be rescheduled? • Are there any near-critical paths? • What risks are on the critical path? • Danglers • No predecessor? • No successor?

  31. Network Analysis (continued) • Analyze against target costs and schedule • Resource usage • Overallocated ? • Availability ?

  32. Making Up Time in a Schedule During Planning • Change the relationships among tasks so that the critical path is shorter (fast tracking) • Do tasks in parallel, instead of sequentially • Contract out tasks that are being done in series because of lack of available personnel • Change approach to work, creating a different set of interrelated tasks with shorter critical path • Change a Finish-Start relationship to a Finish-Finish relationship • Change a date constraint so a task on the critical path can start or end sooner

  33. Leveling Resource leveling • Schedule the project inn such a way as to use resources most effectively • Schedule the project to minimize idle time for resources • Avoid committing resources in such a way that exceeds resource capacity

  34. Leveling (continued) Resource allocation leveling • Distribution of resources to the schedule • Resource constraints vs. time constraints • Priority rules for resource allocation • Examples of resource allocation • Use of analysis of resource histograms

  35. Resource Utilization 1 Weeks

  36. Resource Histogram 1

  37. Review Float

  38. Resource Utilization 2 Weeks

  39. Resource Histogram 2

  40. Rolling-Wave Planning Concept • Detailed planning of entire project may not be practical or possible • Plan finite increments at outset based on project phases (work packages of early efforts, planning packages beyond) • Expand the detailed planning window as each project phase is completed; for longer project phases, plan in increments of 90 days • The planning window will vary based on size, length, complexity, and type of development project (for example, new, derivative, refresh) • Remember to include planning time in project plan

  41. Gantt Chart • Shows start, finish, and duration of various activities • Easiest schedule to make • Most common scheduling tool • Provides tremendous amounts of information - very useful for analysis • Most understandable for people lacking formal project management training • Software capabilities greatly enhance usefulness for analysis

  42. Sample Gantt Chart

  43. Milestone Chart

  44. Before Finalizing Schedule, Examine... Roles: Is there a complete set of roles for each task? • Actions: Add roles where needed People: Who will fill these roles? • Action: Assign people Skills: Do the people assigned possess the needed skills? • Action: Add or change people or re-estimate the duration to allow time to improve skill levels Availability: When will the people really be available? • Action: Reschedule around nonavailable time • Action: Change utilization assumptions to adjust duration • Action: Add more people

  45. Key Messages • Time is usually a critical factor in development projects • A variety of tools can evaluate and map out schedules • Project managers must know how to evaluate their schedules and the potential for schedule improvement

  46. Exercise: Precedence Diagram Method 12 14 8 FS+6 B D G 12 8 14 A H I 16 13 C E 19 SS+10 F

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