project planning

08/04/23 SO1 : Project Management 1

Introduction to Project Planning

Monica Farrow EM [email protected]

www.vision.hw.ac.uk

F29SO1 Software Engineering


Topics today

Work Breakdown Structure Gantt Charts Network Techniques Critical Path Spare time MS Project Resource planning Words of wisdom


Why Plan?

To predict the start or end point of the project To enable communication To highlight problems early To help manage risk

“If you don't plan to succeed, then plan to fail”

anon.


Work Breakdown Structure (WBS)

It is normal to get overwhelmed and confused when beginning to graps the details of even a modest sized project

WBS - A results-organised family tree, the work is split into manageable, logical packages

Make sure packages can be tested for completeness

Moving post-its around on white/black boards can be useful in early discussions.


Simplistic WBS

No concept of time here. WBS will often reflect the chosen SDLC/methodology Should show ALL tasks (including management ones) Tasks should not overlap

Stock Control System

Requirements Design Implement Integrate Maintain

... Build GUI Build Logic Build Database

......


Plans Need Tasks & Tasks Need Durations

Brainstorm tasks Subdivide tasks ‘til each is about 1 or 2 weeks

in duration If you can get down to days then great, but beware of

the need for contingencies (what’s a contingency?)

Tasks (Do not copy these! You are all different): Hand in deliverable 1 (0 days) - A MILESTONE! Develop GUI (10 days) Have ridiculously long Xmas holiday (1 day) …


Milestones

Periodic stages in the project where something measurable should have been achieved.

Highlight these in the plan. The achievement is usually a deliverable, such

as a report or prototype Too often -> they become millstones. Too seldom -> they become worthless. Temper both optimism and pessimism.


Gantt Charts

Named after Henry Gantt. Around since 1st World War


Gantt Charts

Each activity is an element in the WBS Can show critical path

Explained on later slides But not great at showing task precedence Easy for novices to construct and interpret


Dependency/Precedence Relationships

Describe what activities must be done before another activity can take place Boil kettle before adding water to cup Pick up hand set before dialling number Buy computer system before installing it.


Dependency/Precedence Relationships in Gantt chart


Critical Path

The chain of sequential activities that determines the minimum time required for the project.

Passes through activities with least float (spare time)

To examine critical paths and float, we’ll look at network techniques


Network Techniques

Easier to construct than Gantt charts. More difficult for novices to interpret. Often paper based during early planning

activities - easily follows from WBS. Does not rely on your knowledge about task

duration. Does rely on your logical understanding of the

order in which tasks are carried out.


Network Techniques

PERT - Project Evaluation and Review Technique Network based aid for planning and scheduling

related tasks in a large and complex project US Polaris 1958

Captures precedence (walls before roof) and parallel tasks (painting inside and outside – can be done together)

Activity-on-Arrow (AoA) Easier to construct on paper

Activity-on-Node (AoN) Used in many software packages (eg PERT diagrams in MS-

Project) Can be drawn manually in MS Visio


Network Techniques

Activity-on-Arrow (AoA)

1 3

2

4Find Pencil Make Drawing

Find Paper

1 mins 10 mins

2 mins

•Event 3 dependent on 1 & 2•Takes 1 minute to find pencil•Where is the slack here?


Activity-on-Node (AoN)

B depends on A A takes 21 days B starts 5 days after A is complete (-5 would indicate overlap)

Network Techniques

A21

B9

5


Example AoA- Build the network

T1

T3 T4

10

4

8T2

5T7 T8

2finish

F

T57

start

T65

15

C

D EA

T1 10

T2 T1 8

T3 T1 15

T4 T3 4

T5 T1 7

T6 T5 5

T7 T2,T4 5

T8 T7,T6 2


Calculate Critical Path – longest path

T1

T3 T4

10A

4

8T2

5T7 T8

2finish

F

T57

start

T65

For each possible path through the network, calculate the time Start – A – C – D – E – Finish = 10 + 15 + 4 + 5 2 = 36 Start – A – D – E – finish = 10 + 8 + 5 + 2 = 25 Start – A – F – E – finish = 10 + 7 + 5 + 2 = 24

Longest time required is 36 -> this path is the critical path

15

C

D E


T1

10 T3

15

T4

4

T7

5

T2

8

T5

7

T6

5T8

2

The equivalent AoN diagram

ACTIVITY

DURATION


Finding the slack (float)

The next slides show how this diagram can be useful in more complex networks to show clearly

Where the slack (free time) is Which is the critical path

First calculate the earliest possible start and finish times for each activity, by taking a Forwards Pass through each path, following the arrows:

The earliest start (top left) is previous ES plus current Duration The earliest finish (top right) is current ES + Duration The previous EF = the next ES, unless there is a junction At a junction, choose largest previous EF - the next activity

cannot start until all the pre-requisite activities have finished


Forward PassACTIVITY

DURATIONES EF

FLOAT

E = early L = lateS = start F = finish

T1

10 0 10 T3

1510 25

T4

425 29

T7

529 34

T2

810 18

T5

710 17

T6

517 22T8

234 36


Backward Pass

Next, calculate the latest start and finish times for each activity, by following each path backwards along the arrows At the final activity only, set the Latest Finish (LF)

= EF, then follow the arrows backwards The earliest start (ES) = current EF - Duration Other LFs = previous LS, unless there is a

division of paths At a division, choose smallest previous ES


Backward PassACTIVITY

DURATIONES EF

FLOATLS LF

E = early L = lateS = start F = finish

T1

0 10

10 0 10T3

10 25

1510 25

T4

25 29

425 29

T7

29 34

529 34

T2

21 29

810 18

T5

22 29

710 17

T6

29 34

517 22T8

34 36

234 36


Calculate the Slack (Float)

The slack or float is the spare time available for an activity

It is shown in the centre bottom panel It is the difference between the latest possible finish

and the earliest possible finish (LF – EF)

ACTIVITY

DURATIONES EF

FLOATLS LF


Calculate the Slack (Float)

E = early L = late S = start F = finish

ACTIVITY

DURATIONES EF

FLOATLS LF

T1

00 10

10 0 10T3

010 25

1510 25

T4

025 29

425 29

T7

029 34

529 34

T2

1121 29

810 18

T5

1222 29

710 17

T6

1229 34

517 22T8

034 36

234 36


Finding the critical path

The critical path is the one where

Float is always 0

ES = LS and EF = LF

ACTIVITY

DURATIONES EF

FLOATLS LFE = early L = late S = start F = finish

T1

00 10

10 0 10T3

010 25

1510 25

T4

025 29

425 29

T7

029 34

529 34

T2

1121 29

810 18

T5

1222 29

710 17

T6

1229 34

517 22T8

034 36

234 36


Finding the free floatACTIVITY

DURATIONES EF


T1

00 10

10 0 10

T3

010 25

1510 25

T4

025 29

425 29

T7

029 34

529 34

T2

1121 29

810 18

T5

1222 29

710 17

T6

1229 34

517 22T8

034 36

234 36

• Free float is the amount of time a task can be delayed before affecting the timing of the next task.

• It’s only applicable to those tasks immediately preceding a junction


Finding the total floatACTIVITY

DURATIONES EF


T1

00 10

10 0 10

T3

010 25

1510 25

T4

025 29

425 29

T7

029 34

529 34

T2

1121 29

810 18

T5

1222 29

710 17

T6

1229 34

517 22T8

034 36

234 36

• Total float is the spare time available when all preceding activities occur at the earliest possible times and all succeeding activities occur at the latest possible times.

• Same for all activities on an arc – could be split amongst them


Another example

start

C

30 3

A

10 1

B

20 2

E

52 7H

67 13

J

2

I

5

D

41 5

F

4

G

6

ACTIVITY

DURATIONES EF

FLOATLS LF

E = earlyL = lateS = startF = finish

? Critical Path? Float


MS-Project

A widely used tool from Microsoft to help plan projects.

Available in most XP labs. Far more functionality than you’ll need for

your project. Open a new, blank project

The column on the LHS provides excellent guidance

To see it, click on Tasks


MS Project – data entry

Youcreate thelinksAnd add resources

Enter startdate,tasks andduration – start andfinish times calculated


MS Project Gantt chart

Shows hierarchy, precedence, Resources,Milestones


MS Project Network chart


MS Project - schedule

Right click in this box and choose Schedule

Slack and late times are calculated automatically


Final thoughts on MS Project

All sorts of reports exist – experiment with them Use ZoomIn, ZoomOut buttons to change scale

of chart Use Gantt chart wizard to change appearance

When printing, think very hard about what is actually useful e.g. A one-page overview and then more detailed pages is

useful For Gantt charts going over 1 page, use Print

Preview : View tab and tick to print some columns on each page


Resource Management

Examples of resources: technicians designers computer time cash tradesmen vehicles machines


Problems with Resources

usually limited (finite) can’t work on everything at the same time are only available at certain times have other commitments have an associated cost can get sick, go on strike, break down, etc


Resource Management

The quotation here will also apply to other resources, such as hardware, software, etc.

In most cases, managers will have to settle for a less-than-ideal project team – due to budget, availability, and training issues. Sommerville, SE8


Scheduling & Resources

Previously we assumed that we had enough (infinite) resources to complete tasks.

Two extreme cases: Fixed project time scale and infinite resources (time

limited scheduling) Fixed resources, but project duration is flexible

(resource limited scheduling) Most projects are somewhere in-between.


Resource Limited Scheduling

Example Only 2 people available Each activity lasts 5 days A needs 2 staff, B & C need 1. No dependencies.

How best to organise this?

ABC

Staff[2]

Staff

Staff

M T W T F S S M T W T F S S M T W T F S S M T W T F S S M T W03 Apr '00 10 Apr '00 17 Apr '00 24 Apr '00 01 May '00


Time Limited Scheduling

Example The time for a Project can only last 10 days Each activity (A,B,C) lasts 5 days A needs 2 staff @ 5 days each , B & C need 1. C depends on A & B, B depends on A.


ABC

Staff[2]

Staff

Staff

M T W T F S S M T W T F S S M T W T F S S M T W T F S S M T W03 Apr '00 10 Apr '00 17 Apr '00 24 Apr '00 01 May '00


Time & Resource Limited Scheduling

Example A needs 2 staff, B & C need 1. Only 2 people available. Project can only last 10 days. Each activity lasts 5 days C depends on A.



Pragmatic Realities

All projects are unique None will run exactly to plan All involve people Project Management involves change and

decision making - people like neither! Dilbert said “Change is good. You go first!”

A structured approach & tools make things easier

Do not be a slave to your plans They should be living artefacts Change them as necessary


Group Project Scheduling

You are time and resource limited. Resource effort is diluted. Difficult to predict task durations in software

development – estimating needed. Therefore:

Make reasonable guesses and refine these constantly as project progresses.

Build in contingencies. Be prepared for late night heroics!


Answers

Time limited scheduling Project will take 15 days, can improve by adding in

more staff if available / will make a difference Resource limited scheduling

do B & C together before or after A. Shortest possible time is 10 days

• T & R limited• Do A first, then 1 each on B & C simultaneously

project planning

Documents

tasks tasks

network techniques activity

network t1 t3 t4

paper activity

earliest start

finish f t5

f e finish

network techniques easier