3.1 NETWORK Roger D. H. Warburton Determine Activity Dependencies & Critical Path © Kanabar / Warburton,

Objectives 2  Objectives  Understand concepts associated with  Activity Sequencing  Critical Path  Schedule Development

K NOWLEDGE A REA : T IME M ANAGEMENT A subset of project management that includes the processes required to ensure timely completion of the project. It consist of activity definition, activity sequencing, activity duration estimating, schedule development, and schedule control. PMBOK® Guide (PMI) 3

W HERE ARE WE ? InitiationPlanningExecutionClosing Monitor and Control 4

W E C OMPLETED … 5 Collect RequirementsDefine ScopeCreate WBS Scope

WBS “D ECOMPOSITION ” 6 Make Invitations 1.2 Design Print Mail Make Invitations Mail Print Layout Pre-Press 1.2.2

D EVELOPING THE P ROJECT P LAN Add Sequence & Time! 7

T HE P ROJECT N ETWORK A flow chart that graphically depicts the sequence, interdependencies, and start and finish times of the project Leads to a plan of activities that is the critical path through the network 8

F ROM W ORK P ACKAGE TO N ETWORK A BD C Finish Start 9

T HE N ETWORK Start Make Invitations 1.2 Design Print Mail 1.2.3

T HE “A RROW ” D cannot start until A, B, and C have been completed A C BD 11

C ONSTRUCTING A P ROJECT N ETWORK Terminology Activity: An element of the project that requires time A C BD 12

T ERMINOLOGY Path: A sequence of connected, dependent activities. Parallel (Concurrent) Activities: Activities that can occur at the same time. (If desired) C ABD 13

E VENT A point in time when an activity is started or completed. It does not consume time. Milestones are events 14

B URST A CTIVITY An activity that has more than one activity immediately following it (more than one dependency arrow flowing from it). B D A C 15

M ERGE A CTIVITY An activity that has more than one activity immediately following it (more than one dependency arrow flowing from it). B D AC 16

S IMPLE E XAMPLE WITH E VERYTHING ActivityPredecessorTime ANone5 BA15 CA10 DB,C30 B D A C 17

N OTATION Earliest Start ID Identification Earliest Finish SlackDescriptionSlack Latest Start DurationLatest Finish 18

S IMPLE E XAMPLE : 1) F ORWARD P ASS (E ARLIEST ) A 5 C 10 B 15 D 30 ESIDEF SLDesSL LSDurLF 19

S IMPLE E XAMPLE : 1) F ORWARD P ASS (E ARLIEST ) 0A5 5 5C B D50 30 ESIDEF SLDesCr LSDurLF 20

S IMPLE E XAMPLE : 2) B ACKWARD P ASS (L ATEST ) C B D 3050 Delivery Date = 50 0A5 055 ESIDEF SLDesSL LSDurLF 21

S IMPLE E XAMPLE : 3) S LACK = LS - ES 0A C B D = LF - EF C can be delayed by 5 Float 22

S IMPLE E XAMPLE : 4) P ATH OF L EAST S LACK (LS – ES) 0A C B D (+5)= (+20)=

S IMPLE E XAMPLE : 5) C RITICAL P ATH 0A C B D

C RITICAL P ATH The critical path is the network path(s) that has (have) the least slack in common. 25

C RITICAL P ATH the longest path through the network that allows for the completion of all activities the shortest expected time in which the entire project can be completed. Delays on the critical path will delay completion of the entire project. C ABD T=3 T=5 26

C RITICAL P ATH ~ 10% Assign best people to critical activities Prioritize (and eliminate) critical activities Risk assessment on critical activities Visit people working on critical activities Can I borrow Joe? Overtime, technology Schedule changes ± Roll up non criticals C AB D T=3 T=5 27

S IMPLE E XAMPLE : 6) F REE S LACK 0A C B D C Difference between EF and ES that follows it 0 5 Useful! EF – ES 28

B ASIC N ETWORK R ULES Networks typically flow from left to right. An activity cannot begin until all of its predecessor 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 allowed. Conditional statements are not allowed. Use common start and stop nodes. 29

N ETWORK C OMPUTATION P ROCESS Forward Pass—Earliest Times How soon can the activity start? Earliest start—ES How soon can the activity finish? Earliest finish—EF How soon can the project finish? Expected time—ET 30

N ETWORK C OMPUTATION P ROCESS Backward Pass—Latest Times How late can the activity start? Latest start—LS How late can the activity finish? Latest finish—LF Which activities represent the critical path? How long can it be delayed? Slack or float—SL 31

F ORWARD P ASS C OMPUTATION Add 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. 32

B ACKWARD P ASS C OMPUTATION Subtract 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. 33

D ETERMINING S LACK ( OR F LOAT ) Slack (or Float) The amount of time an activity can be delayed after the start of a longer parallel activity or activities. Total slack The amount of time an activity can be delayed without delaying the entire project. 34

I LLOGICAL L OOP A C B 35

I TERATION L OOP Write CH 1 Edit CH 1 ?? 36

A RROWS M AY C ROSS A C B D 37

P RACTICAL C ONSIDERATIONS Network Logic Errors Activity Numbering Use of Computers to Develop Networks Calendar Dates Multiple Starts and Multiple Projects 38

E XAMPLE OF L ADDERING Dig Hole Lay Pipe Fill Hole Dig 1/3 Hole Lay 1/3 Pipe Fill 1/3 Hole Dig 2nd/3 Hole Lay 2nd/3 Pipe Dig 3rd/3 Hole 39

E XTENDED N ETWORK T ECHNIQUES : 1) L ADDERING 100% Complete too restrictive Overlap & long duration Activities are broken into segments so the following activity can begin sooner and not delay the work 40

E XTENDED N ETWORK T ECHNIQUES : 2) L AGS 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. 41

U SE OF L AGS Finish-to-Start Lag Typical: e.g., Ordering Materials Order Activity is 1 day Material takes 5 days to arrive Charge for 1 day Order Assemble 5 Days 42

U SE OF L AGS Start-to-Start Relationship Assemble cannot begin until 5 days after Order begins You can begin Assembly after a portion of Ordering e.g., pipe laying, partial design Order Assemble 5 Days 43

U SE OF L AGS Finish-to-Finish Relationship The finish of Assemble depends on the finish of the Order. Assemble cannot finish any earlier than 5 days after Ordering is complete Order Assemble 5 Days 44

U SE OF L AGS Start-to-Finish Relationship Assemble cannot end until 5 days after Ordering has started. (Because information to Assemble is available after the first 5 days of Ordering.) Order Assemble 5 Days 45

U SE OF L AGS Can be used in Combinations! Assemble cannot begin until 5 days after Ordering has started and Ordering must be finished 3 days before Assemble can be finished. 46

3) H AMMOCK A CTIVITIES An activity that spans over a segment of a project. Duration is determined after the network plan is drawn Used to aggregate sections of the project Facilitates getting the right amount of detail for specific sections of a project. 47

H AMMOCK A CTIVITY E XAMPLE Consulting, Machine Rental, etc. Dig Hole Lay Pipe Patch Pipe Fill Hole Rent Backhoe 48

C ONSTRUCTING A P ROJECT N ETWORK Two Approaches Activity-on-Node (AON) Uses a node to depict an activity. Activity-on-Arrow (AOA) Uses an arrow to depict an activity. 49

AOA E XAMPLE ActivityPredecessorTime ANone5 B A 15 CA10 DB,C30 B D A C A C D 5 B A is 1-2 C is 2-4 D is 4-5 B is

AOA E XAMPLE ActivityPredecessorTime ANone5 BA15 CA10 DB,C30 B D A C A C D 5 B A is 1-2 C is 2-4 D is 4-5 Dummy Activity B is is dummy, zero time 51

AOA Know advantages & Disadvantages Not expect you to do AOA network 52

AON & AOA AONAOA +No Dummy Activities+ Paths simplified +Easier to draw for simple networks + Easier to draw for complex networks +Easily understood by managers + Key events easily flagged −Hard to understand for complex networks − Dummy activities − Emphasizes events, not activities 53

S UMMARY T IME M ANAGEMENT (PMBOK 4 TH E DITION ) 54 Define ActivitiesSequence Activities Estimate Activity Resources Estimate Activity Durations Develop Schedule Time The following are the Time Management Planning Processes

W ORKSHOP Estimate duration for activities Network and Schedule: Generate a MS Project Schedule for the case study

A DDITIONAL R EADING Good overview of Slack is at: us/project/HA aspx us/project/HA aspx 56