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2001ICT - Project Management

Module 8 1

UNIVERSITY2001ICT

2001ICT - Project

Management

Module 8

Building Schedule

UNIVERSITY2001ICT

Reading

Schwalbe Chapters 6

PMBOK Chapter 6

Burrill & Ellsworth Chapters 15 & 16

Cotterell & Hughes Chapters 6 & 8

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Module 8 2

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Review

Software Life Cycle Model

Waterfall, Prototyping, Evolutionary ...

Work Breakdown Structure

Based upon defined process model

Activity Network Diagram

Estimation Principles Functional Size Measurement

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Module Outline

What is Time Management

Time Management Processes

Network Diagrams

Critical Paths

Schedule Management and Control

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Module 8 3

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Project Time Management

Project Time Management includes theprocesses required to ensure timely completionof the project.

These processes interact with each other andwith the processes in the other knowledge areasas well.

Each process may involve effort from one ormore individuals or groups of individuals based

on the needs of the project. Each process generally occurs at least once in

each phase of the project.

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Managing Project Time

ActivityDefinition

ActivitySequencing

ScheduleDevelopment

ScheduleControl

ActivityDuration

Estimating

ActivityResource

Estimating

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Module 8 4

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Time Management Processes

Activity Definitionidentifying the specific activities that mustbe performed to produce the various project deliverables.

Activity Sequencingidentifying and documenting interactivitydependencies.

Activity Resource Estimating - estimating how manyresources a project team should use to perform projectactivities.

Activity Duration Estimatingestimating the number of workperiods which will be needed to complete individual activities.

Schedule Developmentanalyzing activity sequences,

activity durations, and resource requirements to create theproject schedule.

Schedule Controlcontrolling changes to the projectschedule.

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Activity DefinitionWork breakdown structure

Scope statement

Historical information

Constraints

Assumptions

Expert Judgement

Activity list

Supporting detail

Work breakdown structure updates

ActivityDefinition

Activity definition involves identifyingand documenting the specific activitiesthat must be performed in order toproduce the deliverables and sub-deliverables identified in the workbreakdown structure.

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Module 8 5

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Activity Definition

Tools and Techniques Decomposition

Essentially the same as in Scope Definition

The major difference is that this

decomposition results in outputs described as

activitiesrather than as deliverables.

The WBS and the Activity List are usually

developed sequentially:

The WBS is the basis for development of the

final activity list.

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Activity SequencingActivity list

Product description

Mandatory dependencies

Discretionary dependencies

External dependencies

Milestones

Project network diagrams

Activity list updates

ActivitySequencing

Activity sequencing involves identifying anddocumenting interactivity logical relationships.

Activity must be sequenced accurately to supportlater development of a realistic and achievableschedule.

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Module 8 6

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Ordering Tasks

WBS Element Input Output

Task T A B

Sub-task T1 A W

Sub-task T2 W X

Sub-task T3 X Y

Sub-task T4 W Z

Sub-task T5 Y, Z B

T1 T2 T3 T4 T5A B

T1

T2T3

T4 T5

A B

Sequential Ordering

Non-sequential Ordering

T1 T2 T3 T4 T5

T

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Representing an Activity

Network Precedence diagramming method

Nodes represent the Activities

Connections show thedependencies

Arrow diagramming method Arrows represent the activities

Connections at the nodes showdependencies

Conditional diagramming methods Allow for non-sequential activities

(such as loops)

A B C

D E F

Start

A

B

C

D

EF

Finish

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Module 8 7

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The Activity Network Diagram

The Activity Network Diagram is the end-product

of the task decomposition process

It should be accompanied by narrative to explain any

dependencies

It shows the relationships between the tasks that

have to be performed, but says nothing about

how long it will take to perform them

To go further we need to be able to estimatethe

effort, cost and elapsed time for each task or activity

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Activity Resource Estimating

Before estimating activity durations, you musthave a good idea of the quantity and type ofresources that will be assigned to each activity.

Consider important issues in estimatingresources:

How difficult will it be to complete specific activities onthis project?

What is the organizations history in doing similaractivities?

Are the required resources available?

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Module 8 8

UNIVERSITY2001ICT

Activity Duration EstimatingActivity list

Constraints

Assumptions

Resource requirements

Resource capabilities

Historical information

Identified risks

Activity duration estimates

Basis of estimates

Activity list updates

Activity DurationEstimating

Activity duration estimating isthe process of taking informationon the project scope andresources and then developingdurations for input to schedules.

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Estimate Activity Duration

You need to estimate how long it will take tocomplete each activity in the Activity List.

The relationship between effort estimates and

elapsed time is not simple. Calendars, number of personnel, availability of other

resources influence the duration

Use historical data as the basis for estimationwherever possible.

Techniques include: Expert judgment

Analogous estimation

Simulation

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Module 8 9

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Schedule DevelopmentProject network diagrams

Activity duration estimates

Resource requirements

Resource pool description

Calendars

Constraints

Assumptions

Leads and lags

Risk management planActivity attributes

Project Schedule

Supporting detail

Schedule management plan

Resource requirement updates

ScheduleDevelopment

Schedule development means determining startand finish dates for project activities. If the startand finish dates are not realistic, then the projectis unlikely to be finished as scheduled.

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Techniques for Scheduling

Mathematical Analysis Critical Path Method (CPM)

uses single deterministic early and late start and finish dates

for each activity Program Evaluation and Review Technique (PERT)

uses sequential network logic and weighted average durationestimates to calculate project duration

Duration Compression ways to shorten the schedule without changing the

scope

Resource Levelling Heuristics

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Module 8 10

UNIVERSITY2001ICT

Paths in Networks

A path is a sequence of activities that starts with abeginning activity and travels through a series ofimmediate successors until it terminates with an endingactivity

The length of a path is the total time it takes to traversethe path; that is, the total of the durations for theactivities on the path

For any network there is a maximum to the lengths of allthe paths through the network.

Any path whose length is equal to this maximum iscalled a critical path Note that there may be more than one critical paths in a network.

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Calculating the Critical Path

We use a Network

Diagram and label the

nodes to show: Task duration;

Early finish time;

Late finish time;

Slack

ID

S

Slack

LF

Late Finish

EF

Early Finish

D

Duration

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Module 8 11

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Critical Path Method - 1

Calculate Early Start and EarlyFinish Times

The ES for an activity is themaximum of the EF times forall of its immediatepredecessors

The ES for the beginningactivity (I.e. with nopredecessors) is 0.

For each activity, the EF is

equal to the ES plus theduration

Assigning ES and EF timesinvolves making a forwardpassthrough the network.

Activity Duration

A 2

B 4

C 5

D 4

E 6

F 3

2 4 5

4 6 3

2 6

4 10 13

11

130

A B C

D E F

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Calculate Late Start and LateFinish Times

For each activity, the LS is equalto the LF minus the duration

The LF for the ending activity(I.e. with no successors) is thesame as the EF, unless theduration for the entire network isknown.

The LF for an activity is theminimum of the LS times for all ofits immediate successors

Assigning LS and LF timesinvolves making a backward passthrough the network.

Activity Duration

A 2

B 4

C 5

D 4

E 6

F 3

2 4 5

4 6 3

2 6

4 10 13

11

13013

13104

84

A B C

D E F

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Module 8 12

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Calculate Slack

For each activity, the Slack isequal to the Late Finish minusthe Early Finish

(also, Slack - LS - ES)

The slack of an activity is theduration that the activity canbe delayed without delayingthe project, providing it is theonly activity delayed.

Activities that have theminimumslack are those onthe critical path.

Activity Duration

A 2

B 4

C 5

D 4

E 6

F 3

2 4 5

4 6 3

2 6

4 10 13

11

130

13

13104

842

000

2 2

A B C

D E F

UNIVERSITY2001ICT

Why critical paths are important

Slippage of an activity on a critical path results inslippage of the project completion date.

Improvement of the total project duration is most

responsive to improvements along a critical path. It is possible to lengthen non-critical activities without

adverse effect on the project duration.

Critical activities are the ones most in need ofmanagement attention, since their delay most impactsthe project.

Note: the activities on the critical path are not necessarilythe most important activities in the project!

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Module 8 13

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Alternative Dependencies

The standard Critical Path Method is based on simplefinish - start dependencies - ie one task must end beforeanother can begin

Other more complex dependencies are possible: Start to start - one activity cannot start until another starts

End to end - one activity must finish before another can finish

Start to end - one activity must start before another can finish

In each case, it is also possible to identify laggeddependencies.

e.g. Task A cannot start until a specified time after Task Bfinishes.

Good Scheduling Tools allow all of these dependenciesto be recognised.

UNIVERSITY2001ICT

Tools for schedule management

Microsoft Project - Gantt Chart

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Module 8 14

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Tools for schedule management

Microsoft Project - PERT Network

Task A

Start: 4/09/06 ID : 2

F ini sh :5/ 09 /06 D ur : 2d ays

Res:

Task B

Start: 6/09/06 ID: 3

F in ish :11 /0 9/ 06 D ur : 4 da ys

Res:

Task C

Start: 12/09/06 ID: 4

F in ish : 18 /0 9/ 06 D ur : 5 da ys

Res:

Task D

Start: 4/09/06 ID : 5

F ini sh :7/ 09 /06 D ur : 4d ays

Res:

Start

Milestone Date:Mon 4/09/06

ID :1

Task E

Start: 8/09/06 ID: 6

F in ish :15 /0 9/ 06 D ur : 6 da ys

Res:

Task F

Start: 18/09/06 ID: 7

F in ish : 20 /0 9/ 06 D ur : 3 da ys

Res:

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Resource Allocation

Two factors have to be considered in the

allocation of resources:

the resource requirements - the duration of mosttasks is significantly affected by the resources

assigned

the resource capabilities - the duration of most

activities is influenced by the capabilities of the

people assigned to them.

Normally, resources are allocated at the same

time as the network is constructed.

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Module 8 15

UNIVERSITY2001ICT

Resource Limitations

The calculation of critical path assumes

that resources are not constrained.

In the real world constraints always exist.

0

1

23

4

5

6

7

1/01/00 1/02/00 1/03/00

Time

Projec

tStaffing

Theory

Practice

UNIVERSITY2001ICT

Levelling the Project

Different strategies are available to deal

with resource constraints:

Levelling by adjusting Levelling by replanning

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Module 8 16

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Resource levelling -

an example (1)

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Resource levelling -

an example (2)

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Module 8 17

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Schedule ControlProject schedule

Performance reports

Change requests

Schedule management plan

Schedule updates

Corrective action

Lesson learned

ScheduleControl

Schedule control is concerned witha) influencing the factors that create schedule

changes to ensure that changes are agreed upon,b) determining that the schedule has changed, andc) managing the actual changes when and as they

occur.

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Controlling the Schedule

How does a project

get to be six months

late?

Fred Brooks

The Mythical Man Month

One day at a time!

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Module 8 18

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Adjusting the Schedule

Several strategies are available to help

meet constraints on resources:

Extending the project

Slipping activities

Splitting Activities

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Extending the Project

May be the rational response to resourceconstraints

Requires firm credibility in the estimates Move from treating estimation as a political

activity to seeing it as a necessarytechnical task

Even if the project cannot be extended,the arguments may result in moreresources being made available.

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Module 8 19

UNIVERSITY2001ICT

Slipping Activities

General heuristics are available to support scheduleadjustment to meet resource constraints

When slipping activities, start by making use of the slackperiods the difference between slack and float can be important

float is the amount of flexibility in scheduling an activity that willnot affect any other activity

slack also includes adjustments that impact on other activities,but do not affect the overall project duration

If you have to slip activities that are on the critical path,then the overall completion date will be affected

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Choosing the Slippage

How do you choose between several tasks for slippage? ES, EF, LS or LF

Duration

An assigned priority Responsible department

Subnetwork membership

Random selection

Slip activities at random and generate several differentschedules meeting the resource constraints

Select the one that offers the best completion date!

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Module 8 20

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Splitting Activities

Start an activity and pause before

completion

Return and complete the activity when

resources are available

Note that some activities cannot be split!

Splitting tends to confuse people There are overheads associated with

picking up the loose threads

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Replanning the Project

Replan the Activities

re-assign resources

make effective use of resources when thereare surplus

Replan the Network

re-examine the dependencies

it may be possible to perform tasks in parallel

rather than in series

take advantage of partial dependencies

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Module 8 21

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Compressing the Duration

Techniques for duration compression include:

Crashing - analyse cost and schedule trade-offs to

determine how to obtain the greatest compression for

the least incremental cost.

There is not always a viable alternative.

Crashing often results in increased costs.

Fast tracking - performing activities in parallel that

would normally be done in sequence. Start coding before the design is complete

Often results in increased rework

Usually increases risk

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Summary - 1

Starting from the WBS and individual task estimates, we can build anetwork and assign durations to the tasks in the network.

There will usually be a number of different paths through anynetwork. We can calculate the duration of any path; there will

always be a maximum duration for any network. Paths which take this maximum duration are called critical paths Any schedule contains not only the activities and their durations, but

also the identified resources required.

The process of adjusting a schedule to meet resource constraints iscalled resource levelling.

Controlling the schedule may involve a variety of strategies: Extending the project

Slipping activities

Splitting activities

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Exercise

What are the processes involved in Time

Management?

What steps do you use to develop a

schedule?

What is a critical path? Why is it

important?

Documents

2001ict Mo8 Lec