3.1

Dr. Honghui DengDr. Honghui Deng

Associate ProfessorAssociate Professor

MIS DepartmentMIS Department

UNLVUNLV

MIS 746 IS Project Management

3.2

• What are the What are the Three ConstraintsThree Constraints of of Project Management?Project Management?

• What are the Time Killers for Project?What are the Time Killers for Project?

• Is time a resource for project Is time a resource for project management?management?

Q&AQ&A

3.3

• Consider the idea that time is a Consider the idea that time is a resourceresource but also a but also a constraintconstraint for IT for IT project management, project management,

• Is this a contradiction?Is this a contradiction?

DiscussionDiscussion

3.4

Review of PERT/CPMReview of PERT/CPM

Video 5 PERT/CPMVideo 5 PERT/CPM

3.5

PERT/CPMPERT/CPM

PERT (PERT (Program Evaluation Review TechniqueProgram Evaluation Review Technique)/ )/ CPM (CPM (Critical Path MethodCritical Path Method) is a method of ) is a method of scheduling tasks. It shows sequence by scheduling tasks. It shows sequence by detailed activities and time (hours, days, detailed activities and time (hours, days, weeks). It helps determine which task may weeks). It helps determine which task may become a bottleneck and delay the entire become a bottleneck and delay the entire project. PERT is a planning and control tool project. PERT is a planning and control tool that helps accomplish project objectives on that helps accomplish project objectives on time. It graphically illustrates the time. It graphically illustrates the interrelationships of events and activities interrelationships of events and activities required to bring a project to its successful required to bring a project to its successful conclusion. conclusion.

3.6

A management toolA management tool

As a management tool, PERT helps the As a management tool, PERT helps the analysts to analysts to

• CoordinateCoordinate the various project tasks. the various project tasks.• See the See the relative importancerelative importance of each activity. of each activity.• Determine the Determine the timetime to complete each to complete each

activity.activity.• Identify tasks that will Identify tasks that will delaydelay the entire the entire

project if they are not completed as project if they are not completed as scheduled. scheduled.

• RescheduleReschedule activities in order to reduce the activities in order to reduce the total time.total time.

• ControlControl project progressproject progress..

3.7

A network of activitiesA network of activities

PERT is defined in terms of network. The PERT is defined in terms of network. The networknetwork consists of consists of eventsevents and and activitiesactivities. All of the required . All of the required events are connected by arrows that indicate the events are connected by arrows that indicate the preceding and succeeding events. An preceding and succeeding events. An eventevent ( (A, B, C, A, B, C, D, or ED, or E) is the beginning or ending of an activity. An ) is the beginning or ending of an activity. An event can be considered as a event can be considered as a milestonemilestone. Events have . Events have no time dimension and usually are represented by a no time dimension and usually are represented by a circle. An circle. An activityactivity ((presented by an arrowpresented by an arrow)) links two links two successive events together and represents the work successive events together and represents the work required between these two events. An activity must required between these two events. An activity must be accomplished before the following event can be accomplished before the following event can occur. Let’s look at an example. occur. Let’s look at an example.

3.8

A simple exampleA simple example

Consider the list of four activities for Consider the list of four activities for buying a software for your office:buying a software for your office:

Activity Description Immediate predecessors

A Identify needs and a vendor - B Identify the source for funding - C Develop a proposal for funding B D Submit the proposal A,C

The immediate predecessors for any activity are those activities that, when completed, enable the start of that activity.

3.9

Sequence of activitiesSequence of activities

• We can start work on activities A and B We can start work on activities A and B anytime, since neither of these activities anytime, since neither of these activities depends upon the completion of prior depends upon the completion of prior activities.activities.

• C activity cannot start until activity B C activity cannot start until activity B has been completed, and activity D has been completed, and activity D cannot start until both activities A and C cannot start until both activities A and C have been completed.have been completed.

• The graphical representation (next slide) The graphical representation (next slide) is referred to as the PERT/CPM network is referred to as the PERT/CPM network for project.for project.

3.10

Network of four activitiesNetwork of four activities

1 3 4

2

A

B C

D

Arrows indicate project activities

Nodes indicate start and finish of activities

3.11

Another exampleAnother example

Develop the network for a project with Develop the network for a project with following activities and immediate following activities and immediate predecessors:predecessors:

Activity Immediatepredecessors

A - B - C B D A, C E C F C G D,E,F

First, attempt for the first five (A,B,C,D,E) activities

3.12

Network of first five activitiesNetwork of first five activities

1 3 4

2

A

B

C

D

5

E

We need to introduce a dummy activity

3.13

Network of seven activitiesNetwork of seven activities

1 3 4

2

A

B

C

D

5

E

7

6F

G

•Note how the network correctly identifies D, E, and F as the immediate predecessors for activity G.

•Dummy activities can be used to identify precedence relationships correctly as well as to eliminate the possible confusion of two or more activities having the same starting and ending nodes.

3.14

Scheduling with activity timeScheduling with activity time

Activity Immediate Completionpredecessors Time (week)

A - 5 B - 6 C A 4 D A 3 E A 1 F E 4 G D,F 14 H B,C 12 I G,H 2

Total …… 51

This information indicates that the total time required to complete activities is 51 weeks. However, we can see from the network that several of the activities can be carried out simultaneously (A and B, for example).

3.15

Network with activity timeNetwork with activity time

1

3

4

2 5

7

6

A 5

B6

C4

D3

E1

F4

G14

H12

I2

Each activity letter is written above and each activity time is written bellow the arc

To complete the total project completion time we will have to analyze the network and identify what is called critical path. A path is a sequence of connected activities that leads from the starting node (1) to the completion node (7).

3.16

Earliest start & earliest finish timeEarliest start & earliest finish time

• We are interested in the longest path through We are interested in the longest path through the network, i.e., the critical path.the network, i.e., the critical path.

• Starting at the network’s origin (node 1) and Starting at the network’s origin (node 1) and using a starting time of 0, we compute an using a starting time of 0, we compute an earliest startearliest start (ES) and (ES) and earliest finishearliest finish (EF) time for (EF) time for each activity in the network.each activity in the network.

• The expression The expression EF = ES + tEF = ES + t can be used to can be used to find the earliest finish time for a given activity. find the earliest finish time for a given activity. For example, for activity A, ES = 0 and t = 5; For example, for activity A, ES = 0 and t = 5; thus the earliest finish time for activity A is thus the earliest finish time for activity A is

EF = 0 + 5 = 5EF = 0 + 5 = 5

3.17

Arc with ES & EF time Arc with ES & EF time

1

2

A [0,5]

5

Activity

ES = earliest start time

ES = earliest finish time

t = expected activity time

3.18

Network with ES & EF timeNetwork with ES & EF time

1

3

4

2 5

7

6

A[0,5

] 5

B[0,6] 6

C[5,9]

4

D[5,8] 3

E[5,6] 1 F[6,10

]

4

G[10,24]

14 H[9,21]

12

I[24,26]

2

Earliest start time rule: The earliest start time for an activity leaving a particular node is equal to the largest of the earliest finish times for all activities entering the node.

3.19

Latest start & latest finish timeLatest start & latest finish time

• To find the critical path we need a To find the critical path we need a backward backward pass calculationpass calculation. .

• Starting at the completion point (node 7) and Starting at the completion point (node 7) and using a using a latest finishlatest finish time (LF) of 26 for activity I, time (LF) of 26 for activity I, we trace back through the network computing we trace back through the network computing a a latest startlatest start (LS) and latest finish time for each (LS) and latest finish time for each activity. activity.

• The expression The expression LS = LF – tLS = LF – t can be used to can be used to calculate latest start time for each activity. For calculate latest start time for each activity. For example, for activity I, LF = 26 and t = 2, thus example, for activity I, LF = 26 and t = 2, thus the latest start time for activity I is the latest start time for activity I is

LS = 26 – 2 = 24LS = 26 – 2 = 24

3.20

Network with LS & LF timeNetwork with LS & LF time

1

3

4

2 5

7

6

A[0,5

] 5

[0,5

]

B[0,6] 6[6,12]

C[5,9]

4[8,12]

D[5,8]3[7,10]

E[5,6]1[5,6]F[6

,10]

4[6,1

0]

G[10,24]

14[10,24] H[9,21]

12[12,24]

I[24,26]

2[24,26]

Latest finish time rule: The latest finish time for an activity entering a particular node is equal to the smallest of the latest start times for all activities leaving the node.

3.21

Activity, duration, ES, EF, LS, LFActivity, duration, ES, EF, LS, LF

2

3

C [5,9]

4 [8,12]

Activity

ES = earliest start time

EF = earliest finish time

LF = latest finish timeLS = latest start time

3.22

Slack or free timeSlack or free time

Slack = LS – ES = LF – EFSlack = LS – ES = LF – EF

Slack is the length of time an activity can be Slack is the length of time an activity can be delayed without affecting the completion date delayed without affecting the completion date for the entire project. For example, for the entire project. For example,

slack for slack for C = LS – ES = 8 – 5 = 3 weeksC = LS – ES = 8 – 5 = 3 weeks

or or LF – EF = 12 – 9 = 3 weeksLF – EF = 12 – 9 = 3 weeks..

This means activity C can be delayed up to 3 This means activity C can be delayed up to 3 weeks (start anywhere between weeks 5 and weeks (start anywhere between weeks 5 and 8).8).

3.23

Activity schedule for our exampleActivity schedule for our example

ActivityActivity Earliest Earliest start (ES)start (ES)

Latest Latest start (LS)start (LS)

Earliest Earliest finish finish (EF)(EF)

Latest Latest finish finish (LF)(LF)

SlackSlack(LS-ES)(LS-ES)

Critical Critical pathpath

AA 00 00 55 55 00 YesYes

BB 00 66 66 1212 66

CC 55 88 99 1212 33

DD 55 77 88 1010 22

EE 55 55 66 66 00 YesYes

FF 66 66 1010 1010 00 YesYes

GG 1010 1010 2424 2424 00 YesYes

HH 99 1212 2121 2424 33

II 2424 2424 2626 2626 00 YesYes

3.24

Important questionsImportant questions

• What is the total time to complete the project?What is the total time to complete the project?– 26 weeks if all individual activities are completed on

schedule.

• What are the scheduled start and completion What are the scheduled start and completion times for each activity?times for each activity?– ES, EF, LS, LF are given for each activity.

• What activities are What activities are criticalcritical and must be and must be completed as scheduled in order to keep the completed as scheduled in order to keep the project on time?project on time?– Critical path activities: A, E, F, G, and I.

• How long can How long can non-criticalnon-critical activities be delayed activities be delayed before they cause a delay in the project’s before they cause a delay in the project’s completion timecompletion time– Slack time available for all activities are given.