network diagram

PROJECT COSTRUCTION MANGEMENT

DEVELOPING THE PROJECT NETWORK

DEVELOPING THE PROJECT NETWORK

The project network is the tool used for planning, scheduling and monitoring project progress.

The network depicts the project activities that must be completed, the logical sequences, the interdependencies of the activities to be completed and in most cases the time for the activities to start and finish along with the longest path through the network-CRITICAL PATH.

DEVELOPING THE PROJECT NETWORK

The network is the framework for the project information system that will be used by the project managers to make decisions concerning project time, cost and performance.

DEVELOPING THE PROJECT NETWORK

Project networks minimize surprises by getting the plan out early and allowing corrective feedback.

FROM WORK PACKAGE TO NETWORK

Project networks are developed from the WBS.

Project network is a visual flow diagram of the sequence, inter relationships and dependencies of all the activities that must be accomplished to completed the project.

FROM WORK PACKAGE TO NETWORK

Activity is an element in the project that consumes time-for example, work or waiting.

Work packages from the WBS are used to build the activities found in the project network.

An activity can include one or more work packages.

FROM WORK PACKAGE TO NETWORK

Networks are built using nodes (boxes) and arrow ( lines ).

Node represents activity

Arrow represents dependency and project flow

CONSTRCUTING A PROJECT NETWORK

Terminology:Activity : It is an element of the project that

requires time. Activities usually represent one or more tasks from a work package.

Merge Activity: this is an activity that has more than one activity immediately preceding it (more than one dependency arrow flowing to it).

Parallel Activities: activities that can take place at the same time, if the manager wishes.

Path: A sequence of connected dependent activities.

Critical Path: the longest path through the network.

APPROACHES

The two approaches used to develop project networks are known as activity on node (AON) and activity on arrow (AOA).

AON method has come to dominate most projects.

BASIC RULES TO FOLLOW IN DEVELOPING PROJECT NETWORKS Networks flow typically from left to right.

An activity cannot begin until all preceding connected activities have been completed.

Arrows on networks indicate precedence and flow. Arrows can cross over each other.

Each activity should have a unique identification number

An activity identification number must be larger that that of any activities that precede it.

Looping is not allowed ( recycling through a set of activities)

Conditional statements are not allowed ( if successful, do something, if not, do nothing )

Experience suggests that when there are multiple starts a common start node can be used to indicate a clear project beginning on the network similarly ending.

AON FUNDAMENTALSAON method is also sometimes called

precedence diagramming method.

Activity is represented by a node (box)

The dependencies among activities are depicted by arrows

Arrows indicate how the activities are related and the sequence in which things must be accomplished.

AON FUNDAMENTALSActivities that must be completed immediately

before an activity are called predecessor activities.

Activities that must immediately follow an activity are called successor activities.

Activities that can occur while another activity is taking place is known as concurrent or parallel activities.

A B C

X

Y

Z

J

K

L

M

X

Y

Z

AA

CLASS ASSIGNMENT KOLL BUSINESS CENTRE

ACTIVITY DESCRIPTION PRECEDING ACTIVITY

A APPLICATION APPROVAL

NONE

B CONSTRUCTION PLANS

A

C TRAFFIC STUDY A

D SERVICE AVALIABLITY

A

E STAFF REPORT B,C

F COMMISION APPROVAL

B,C,D

G WAIT FOR CONSTRUCTION

F

H OCCUPANCY E,G

NETWORK COMPUTATION PROCESS

Performing a few simple computations allows the project manager to complete a process known as the forward and backward pass.

Completion of the forward and backward pass will answer the following questions:

Forward pass:How soon can the activity start? Early start- ESHow soon can the activity finish? Early finish- EFHow soon can the project be finished? Expected

Time-TE

NETWORK COMPUTATIONS

Backward pass:How late can the activity start? Late start- LSHow late can the activity finish? Late finish- LFWhich activities represent the critical path?How long the project can be delayed? Slack or

float-SL

FORWARD PASSForward pass starts with the first project activity

( ies ) and traces each path through the network to the last project activity ( ies ).

As you can trace along the path, you add the activity times. The longest path denotes the project completion time for the plan and is called the critical path (CP).

FORWARD PASS KOLL BUSINESS CENTER

ACITVITY DESCRIPTION PRECEDING ACTIVITY

ACTIVITY TIME

A APPLICATION APPROVAL

NONE 5

B CONSTRUCTION PLANS

A 15

C TRAFFIC STUDY A 10

D SERVICE AVALIABLITY

A 5

E STAFF REPORT B,C 15

F COMMISION APPROVAL

B,C,D 10

G WAIT FOR CONSTRUCTION

F 170

H OCCUPANCY E,G 35

ES

SL

LS

ID

DUR

EF

LF

DESCRIPTION

FORWARD PASSYou add activity times along each path in the

network ( ES + Dur = EF )

You 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 this case you select the largest early finish number (EF) of all its immediate predecessor activities.

BACKWARD PASSThe backward pass starts with the last project

activity on the network. You trace backward on each path subtracting activity times to find the late start LS and late finish times LF for each activity. Before backward pass can be computed , the late finish for the last project activity must be selected.

This time is usually set equal to the EF of the last project activity or in case of multiple finish activities the activity with the largest EF.

BACKWARD PASSYou subtract activity times along each path

starting with the project end activity ( LF – Dur = LS)

You carry the LS to the next preceding activity to establish its LF, unless

The next preceding activity is a burst activity; in this case you select the smallest LS of all its immediate successor activities to establish its LF

BACKWARD PASSKOLL BUSINESS CENTER

ACITVITY DESCRIPTION PRECEDING ACTIVITY

ACTIVITY TIME

A APPLICATION APPROVAL

NONE 5

B CONSTRUCTION PLANS

A 15

C TRAFFIC STUDY A 10

D SERVICE AVALIABLITY

A 5

E STAFF REPORT B,C 15

F COMMISION APPROVAL

B,C,D 10

G WAIT FOR CONSTRUCTION

F 170

H OCCUPANCY E,G 35

ES

SL

LS

ID

DUR

EF

LF

DESCRIPTION

DETERMINING SLACK(FLOAT)

It is possible to determine which activities can be delayed by computing “slack” or “float”.

Total slack or float for an activity is simply the difference between the LS and ES or between the LF and EF

Total slack tells us the amount of time an activity can be delayed and yet not delay the project.

DETERMINING SLACK (FLOAT)

After the slack for each activity is computed, the critical path is easily identified.

When the LF = EF for the end project activity, the critical path can be identified as those activities that also have LF = EF or a slack of zero LF- EF = 0

The critical path is the network path that has the least slack in common

CLASS ASSIGNMENT ID DESCRIPTION PREDECESSO

RTIME

A EXTERNAL SPECIFICATION NONE 8

B REVIEW DESIGN A 2

C DOCUMENT NEW FEATURES A 3

D WRITE SOFTWARE A 60

E PROGRAM AND TEST B 60

F EDIT AND PUBLISH NOTES C 2

G REVIEW MANUAL D 2

H ALPHA SITE E,F 20

I PRINT MANUAL G 10

J BETA SITE H,I 10

K MANUFACUTRE J 12

L RELEASE AND SHIP K 3

FORWARD PASS?

BACKWARD PASS?

SLACK?

CRITICAL PATH?

THREE POINT ESTIMATION EXAMPLE

Q1: Moon Travels are planning on implementing a travel booking system. In the past they were using a completely manual system, which caused errors and delays for their customers. The project manager is confident that the implementation will be completed in 6 weeks, with a most optimistic estimate being 4 weeks, and the worst case scenario might take it to 11 weeks. What must be the three point estimate for this travel booking system implementation?

A: 4 weeksB: 6 weeksC: 11 weeksD: None of the Above.

THREE POINT ESTIMATION EXAMPLE

Q2: You are the project manager of Libra Travels SSS Project.  You have decided to use the 3 point estimation technique for his project. For the “Test Corporate Bookings” activity, the following estimates are available. O=4, P=9, M=5. What is the result of this estimate?

A: 5.5 weeksB: Eighteen weeksC: 33.33 DaysD: Three weeks