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Chap 6 Developing A Project Plan
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- 2. Developing the ProjectPlan The Project Network A flow chart that graphically depicts the sequence, interdependencies, and start and finish times of the project job plan of activities that is the critical path through the network Provides the basis for scheduling labor and equipment Provides an estimate of the project’s duration Provides a basis for budgeting cash flow Highlights activities that are “critical” and should not be delayed Help managers get and stay on plan
- 3. From Work Package…FIGURE 6.1 WBS/Work Package- Sample
- 4. … to NetworkFIGURE 6.1 (cont’d) Network based on prior WBS Sample
- 5. Constructing a ProjectNetwork Terminology Activity: an element of the project that requires time. Merge activity: an activity that has two or more preceding activities on which it depends. Parallel (concurrent) activities: Activities that can occur independently and, if desired, at the same time…or not A C B D
- 6. Constructing a ProjectNetwork (cont’d) Terminology Path: a sequence of connected, dependent activities. Critical path: the longest path through the activity network that allows for the completion of all project-related activities; It is also the shortest expected time in which the entire project can be completed. Delays on the critical path will delay completion of the entire project. D (Assumes that minimum of A + B > minimum of C in length of times to complete activities.) C A B
- 7. Terminology Event: a point in time when an activity is started or completed. It does not consume time. Burst activity: an activity that has more than one activity immediately following it (more than one dependency arrow flowing from it). Two Approaches to Networks Activity-on-Node (AON) Uses a node to depict an activity Used in Software Industry Activity-on-Arrow (AOA) Uses an arrow to depict an activity Traditional in Construction Constructing a Project Network (cont’d) B D A C
- 8. AoA vs. AoNFundamental difference in philosophy DS856 will use only AoN because it: … Emphasizes the process (i.e. QA) more than the end result … dominates in more Bay Area relevant industries (software and consulting) AoA is only in the text’s appendix Is supported by MSProject Lends itself to “post-it notes on the whiteboard” brainstorming Doesn’t require use of “dummy activities” or other confusing conceits Can duplicate an AoA network through use milestones and deliverables
- 9. Basic Guidelines toFollow in Developing Project Networks Networks typically flow from left to right. An activity cannot begin until all of its activities are complete. Arrows indicate precedence and flow and can cross over each other. Identify each activity with a unique number; this number must be greater than its predecessors. Looping is not possible! Conditional statements are not allowed. Use common start and stop nodes.
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- 11. Activity-on-Node Fundamentals (cont’d)FIGURE 6.2 (cont’d)
- 12. Example: Post-it WeddingBelow are a set of tasks and durations for a wedding. Break into groups of 3-5 and create a project network. Put in a start and end activity 1 wk Sent Invitations to Guests SI 2 days Select Grooms Tux GT 6 wks Collect RSVPs CR 3 wks Select Site&Date SS 1 wk Tell Caterer headcount & Order food OF 2 wks Hire Caterers HC 1 wk Hire Officiant HO 4 wks Get Bridemaids' Dresses altered BA 4 days Pick Menu PM 4 wks Shop for Wedding Gown SG 2 wks Order Flowers FL 4 wks Select Bridesmaids Dresses BD 3 wks Audition Mariachi Bands MB 2 wks Get Wedding Gown altered GA 2 days Select Best Man&Usher's Tuxes UT 6 wks Bride goes on Diet DI 1 wk Select and Sign on Band SB 2 wks Order Invitations OI Duration Description abrev Duration Description abrev
- 13. Network Information: ExampleTABLE 6.1 Let’s build the structure first…
- 14. Koll Business Center—Complete Network FIGURE 6.4
- 15. Network Computation ProcessForward Pass —Earliest Times How soon can the activity start? (early start—ES) How soon can the activity finish? (early finish—EF) How soon can the project finish? (expected time—ET) Backward Pass —Latest Times How late can the activity start? (late start—LS) How late can the activity finish? (late finish—LF) Which activities represent the critical path? How long can it be delayed? (slack or float—SL)
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- 18. Forward Pass ComputationAdd activity times along each path in the network (ES + Duration = EF). Carry the early finish (EF) to the next activity where it becomes its early start (ES) unless… The next succeeding activity is a merge activity, in which case the largest EF of all preceding activities is selected.
- 19. Activity-on-Node Network ForwardPass FIGURE 6.6
- 20. Backward Pass ComputationSubtract activity times along each path in the network (LF - Duration = LS). Carry the late start (LS) to the next activity where it becomes its late finish (LF) unless... The next succeeding activity is a burst activity, in which case the smallest LF of all preceding activities is selected.
- 21. Activity-on-Node Network BackwardPass FIGURE 6.7 Don’t panic!- the ES-EF boxes are still filled in, but this diagram is just emphasizing how to get LS and LF
- 22. Activity-on-Node Network withSlack FIGURE 6.8 Now that we have LS,LF in addition to EF, ES, we can fill LAST box in
- 23. Another Way toFind Slack- The Gantt Chart Once activity precedence and durations are established, we can determine the critical path and slack via a gantt chart. Gantt charts can be hand-drawn, but practitioners generally use MS-Project .
- 24. Determining Slack (Not All Slack is Equal) Free Slack (or Float) The amount of time an activity can be delayed without delaying connected successor activities Tends to happen as the last activity in a path before a merge activity (when another path is the critical one). Total Slack The amount of time an activity can be delayed without delaying the entire project The critical path is the network path(s) that has (have) the least slack in common. This class will avoid the confusion of negative slack! … thus all projects will have their end activity have LF=EF So all critical path activities will have a total slack of 0.
- 25. Slack and Slackers:The Simplest Example of Free Slack Take a 5 person marketing project –Team5 Remy writes the requirements doc- which will take 2 days Polly can build the prototype from the requirements doc in 7 days Su needs 3 days to survey potential consumers once he has the requirements doc. Al gets to analyze the consumer responses to the survey, which will take 2 days. Fatima prepares the final presentation to management, so she needs the prototype and the analysis from the survey. This will take 2 days. Which activities are: Critical Have total slack but not free slack Have free slack Who can disappear for a day in the middle of their project and annoy the fewest people?
- 26. Extended Network Techniques to Come Close to Reality Laddering Activities are broken into segments so the following activity can begin sooner and not delay the work. Lags The minimum amount of time a dependent activity must be delayed to begin or end Lengthy activities are broken down to reduce the delay in the start of successor activities. Lags can be used to constrain finish-to-start, start-to-start, finish-to-finish, start-to-finish, or combination relationships. MS project defaults to finish-to-start, but represents all the others, as well…
Editor's Notes
- #3 WBS is hierarchical, Network is sequential, emphasizing interdependencies
- #5 Above is by WBS code, below is by description, presumably with a duration
- #8 Lets us do the post it activities bettter as well, wherein each activity is a
- #10 Much of this should be review from BUS786…. Fun activity- if not sure of sequences for activities, can put activities on post its and then move them around. (another reason to use AoN)
- #13 People may have some different dependencies Use the post its- (have people write the ID and durations on and as much of description as appropriate) Break into teams, give them 5 minutes to come up with an order. Find a volunteer team to present- see if others agree or disagree. Make changes as needed. Save one for future illustration
- #14 Can do a network- examples later
- #17 Now we are going to use the AON we did before to compute Slack by hand.
- #18 Start with first activities, fill in top (ES, EF). Convention is start at 0.
- #20 Don’t need to bother putting numbers on the arrows that are the sole arrow going into a node, in fact # on arrows are optional
- #25 Free slack typically occurs at the end of a path that feeds into a merge activity where another feeder is the critical path The whole ES-EF-LS-LF algorithm does not capture Free Slack, only Total Slack. Use MS Project.
- #26 Draw the AoN Network. CP R-D-F 11 days R-S-A-F 9 days- 2 days total slack for A,S, but only A has free slack. If S disappears for a day without telling anyone, A will be annoyed. Project won’t be late. However, if R,P, or F disappear for a day, the project is delayed as these are critical activities!