Developingaproject Network

Copyright Copyright © © 2006 The McGraw-Hill Companies. All rights reserved. 2006 The McGraw-Hill Companies. All rights reserved. McGraw-Hill/Irwin 6McGraw-Hill/Irwin 6––11

Developing a Developing a Project PlanProject Plan

Developing a Developing a Project PlanProject Plan


Developing the Project PlanDeveloping the Project PlanDeveloping the Project PlanDeveloping the Project Plan

• 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


From Work Package…From Work Package…From Work Package…From Work Package…

FIGURE 6.1

WBS/Work Package- Sample


……to Networkto Network……to Networkto Network

FIGURE 6.1 (cont’d)

Network based on prior WBS Sample


Constructing a Project NetworkConstructing a Project NetworkConstructing a Project NetworkConstructing a Project Network

• Terminology

–Activity: an element of theproject 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


Constructing a Project Network (cont’d)Constructing a Project Network (cont’d)Constructing a Project Network (cont’d)Constructing a Project Network (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

C

A B

(Assumes that minimum of A + B > minimum of C in length of times to complete activities.)


• 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

B

D

A C

Constructing a Project Network (cont’d)Constructing a Project Network (cont’d)


Basic Guidelines to Follow in Developing Project Basic Guidelines to Follow in Developing Project NetworksNetworks

Basic Guidelines to Follow in Developing Project Basic Guidelines to Follow in Developing Project NetworksNetworks

• 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.


Activity-on-Node FundamentalsActivity-on-Node FundamentalsActivity-on-Node FundamentalsActivity-on-Node Fundamentals

FIGURE 6.2


Activity-on-Node Fundamentals (cont’d)Activity-on-Node Fundamentals (cont’d)Activity-on-Node Fundamentals (cont’d)Activity-on-Node Fundamentals (cont’d)

FIGURE 6.2 (cont’d)


A Comparison of AON and AOA Network A Comparison of AON and AOA Network ConventionsConventions


Activity on Activity Activity onNode (AON) Meaning Arrow (AOA)

A comes before B, which comes before C

(a) A B CBA C

A and B must both be completed before C can start

(b)

A

CC

B

A

B

B and C cannot begin until A is completed

(c)

B

A

CA

B

CFigure 3.5Figure 3.5





C and D cannot begin until both A and B are completed

(d)A

B

C

D B

A C

D

C cannot begin until both A and B are completed; D cannot begin until B is completed. A dummy activity is introduced in AOA

(e)CA

B D

Dummy activityA

B

C

D

Figure 3.5Figure 3.5





B and C cannot begin until A is completed. D cannot begin until both B and C are completed. A dummy activity is again introduced in AOA.

(f)

A

C

DB A B

C

D

Dummy activity



AON Example AON Example AON Example AON Example

Activity DescriptionImmediate

Predecessors

A Build internal components —

B Modify roof and floor —

C Construct collection stack A

D Pour concrete and install frame A, B

E Build high-temperature burner C

F Install pollution control system C

G Install air pollution device D, E

H Inspect and test F, G

Milwaukee Paper Manufacturing'sMilwaukee Paper Manufacturing'sActivities and PredecessorsActivities and Predecessors

Table 3.1Table 3.1


AON Network for Milwaukee PaperAON Network for Milwaukee PaperAON Network for Milwaukee PaperAON Network for Milwaukee Paper

A

Start

BStart Activity

Activity A(Build Internal Components)

Activity B(Modify Roof and Floor)





C

D

A

Start

B

Activity A Precedes Activity C

Activities A and B Precede Activity D



G

E

F

H

CA

Start

DB

Arrows Show Precedence Relationships



HH

(Inspect/ (Inspect/ Test)Test)

77Dummy Dummy ActivityActivity

AOA Network for Milwaukee PaperAOA Network for Milwaukee PaperAOA Network for Milwaukee PaperAOA Network for Milwaukee Paper

66

FF(Install

(Install

Controls)

Controls)EE

(Bu

ild B

urn

er)(B

ui ld

Bu

rner)

GG

(Insta

ll

(Insta

ll

Pollutio

n

Pollutio

n

Device)

Device)

55DD

(Pour (Pour Concrete/ Concrete/

Install Frame)Install Frame)

44CC

(Construct (Construct Stack)Stack)

11

33

22

BB(Modify

(Modify

Roof/Floor)

Roof/Floor)

AA(B

uild In

tern

al

(Build

Inte

rnal

Componen

ts)

Componen

ts)



Example: Post-it WeddingExample: Post-it WeddingExample: Post-it WeddingExample: Post-it Wedding

• Below 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

abrev Description Duration abrev Description Duration

OI Order Invitations 2 wks SB Select and Sign on Band 1 wk

DI Bride goes on Diet 6 wks UT Select Best Man&Usher's Tuxes 2 days

GA Get Wedding Gown altered 2 wks MB Audition Mariachi Bands 3 wks

BD Select Bridesmaids Dresses 4 wks FL Order Flowers 2 wks

SG Shop for Wedding Gown 4 wks PM Pick Menu 4 days

BA Get Bridemaids' Dresses altered 4 wks HO Hire Officiant 1 wk

HC Hire Caterers 2 wks OF Tell Caterer headcount & Order food 1 wk

SS Select Site&Date 3 wks CR Collect RSVPs 6 wks

GT Select Grooms Tux 2 days SI Sent Invitations to Guests 1 wk


Network Information: ExampleNetwork Information: ExampleNetwork Information: ExampleNetwork Information: Example

TABLE 6.1

Let’s build the structure first…


Koll Business CenterKoll Business Center—Complete Network—Complete NetworkKoll Business CenterKoll Business Center—Complete Network—Complete Network

FIGURE 6.4


Network Computation ProcessNetwork Computation ProcessNetwork Computation ProcessNetwork Computation Process

• Forward 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)


Network InformationNetwork InformationNetwork InformationNetwork Information

TABLE 6.2


Activity-on-Node NetworkActivity-on-Node NetworkActivity-on-Node NetworkActivity-on-Node Network

FIGURE 6.5


Forward Pass ComputationForward Pass ComputationForward Pass ComputationForward Pass Computation

• 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.


Activity-on-Node Network Forward PassActivity-on-Node Network Forward PassActivity-on-Node Network Forward PassActivity-on-Node Network Forward Pass

FIGURE 6.6


Backward Pass ComputationBackward Pass ComputationBackward Pass ComputationBackward Pass Computation

• 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.


Activity-on-Node Network Backward PassActivity-on-Node Network Backward PassActivity-on-Node Network Backward PassActivity-on-Node Network Backward Pass

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


Activity-on-Node Network with SlackActivity-on-Node Network with SlackActivity-on-Node Network with SlackActivity-on-Node Network with Slack

FIGURE 6.8

Now that we have LS,LF in addition to EF, ES, we can fill LAST box in


Another Way to Find Slack-Another Way to Find Slack- The Gantt Chart The Gantt Chart

Another Way to Find Slack-Another Way to Find Slack- The Gantt Chart 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.


Determining Slack Determining Slack (Not All Slack is Equal)(Not All Slack is Equal)Determining Slack Determining Slack

(Not All Slack is Equal)(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.


Slack and Slackers: The Simplest Example of Slack and Slackers: The Simplest Example of Free SlackFree Slack

Slack and Slackers: The Simplest Example of Slack and Slackers: The Simplest Example of Free SlackFree 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:

1. Critical2. Have total slack but not free slack3. Have free slack

• Who can disappear for a day in the middle of their project and annoy the fewest people?


Extended Network Techniques Extended Network Techniques to Come Close to Realityto Come Close to Reality

Extended Network Techniques Extended Network Techniques to Come Close to Realityto 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…

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Developingaproject Network