Project Scheduling Tools As part of CSA3040 © 2003, 2004 – Dr. Ernest Cachia

Project Scheduling Tools

As part of CSA3040

© 2003, 2004 – Dr. Ernest Cachia

Sep. 2003 (C) 2003 - Dr. Ernest Cachia Slide 2

Project Schedule Components

ActivitiesResources (including the human type)Time (durations and deadlines)ProductsSequenceChecks


The Problem

Scheduling requires strict planning and a fair amount of prognosis

There are many factors that determine a schedule (see previous slide)

Getting all the aspects of a schedule rightly concerted is a very difficult task – even for relatively small projects

Scheduling is of paramount importance in project management

Therein lies the problem!


A Solution

Techniques and supporting tools


Activity Network Diagrams

Practically the same

A more modern variationof PERT and CPM

Available in two flavours Activity-On-Arrow (AOA) Activity-On-Node (AON)

Diagram type names PERT (Program Evaluation Review Technique) CPM (Critical Path Method) PN (Precedence Network)

AOA: PERT and CPMAON: Precedence Networks

Not part of the NCC BCISsyllabus


AOA Diagrams

Diagram components (symbols) Nodes (drawn as circles) Links (drawn as directed arcs)

Symbol meanings Nodes: Start/Stop events (points) Links: Activities


AOA Diagrams Construction Rules

Must contain only one start and one end node A link has duration (optionally shown) A node has no duration (simply start/stop point) Time flows from left to right Nodes are numbered sequentially Loops are not allowed (by concept) Dangles are not allowed (except in the case of

the one and only end node)


AOA Diagram Example (1/2)

1 2 3

4

5 6A

B

C

D

F

E

G

H

Explanation:The above project (or part of) consists of eight activities (“A”~“H”). The duration of each activity is not indicated. The project starts at node one and ends at node six. The derived duration of activity “A” is the time difference between node two and node one; the derived duration of activity “B” is the time difference between node four and node 1; and so on.


AOA Diagram Example (2/2)

1

3

2

4

5

Readsources

Start wordprocessor

Type personalnotes

Write somerev. questions

. . . . . .

Explanation:There are four activities in all. A student reads from various sources and starts a word-processor to then type in some personal notes and furthermore, manually writes some questions on paper to remember to ask the lecturer. IN PRACTICE reading and writing questions can proceed separately from starting the word processor to type in some personal notes. THEREFORE…


Separating Activity Paths (from example on previous slide)

1 3

2

4

5

Readsources

Start wordprocessor

Type personalnotes

Write somerev. questions

. . . . . .

3a

Dummy link

Please note, that a dummy link has zero duration time and uses absolutely no resources.


Lagged Parallel Activities

To show the delayed start/finish of parallel activity sequences.

1 3

2

Get client feedbackon first prototype

Develop secondprototype

5

3 days1 day. . . . . .


Labelling Activities (PERT Style)

One way:

A simpler way:

ID

Earliestdate

Latestdate

Slack

Earliestdate

Latestdate


Scheduling Analysis (using PERT)

Example(taken from Hughes)

Initial activity network:

1

???

2

???

3

???

4

???

6

???

5

???

A

B

C

D

E

F

G

H

Activity Duration (weeks) Precedents

A: H/W selection 6B: S/W design 4C: Install H/W 3 AD: Code/Test S/W 4 BE: Data input 3 BF: User manuals 10G: User training 3 E,FH: Install/Test sys. 2 C,D

Project schedule specification table:


Rule: The earliest date for an event is the earliest finish date for all activities ending at that event. Where common ending activities are present, the latest of the earliest finish dates is taken.

Start date for A, B, F = 0. If duration of A = 6 weeks (see project schedule

specification table), then earliest date for event 2 is 6 weeks.

If duration of B = 4, then earliest date for event 3 is 4 weeks.

And so on, simply adding on the weeks from one event to the next on every path through the network

This will produce the diagram on the next slide…

Analysis: The “Forward Pass”


Resulting from the “Forward Pass”

1

??0

2

??6

3

??4

4

??9

6

??13

5

??10

A=6

B=4

C=3

D=4

E=3

F=10

G=3

H=2

This is the resulting diagram from a “forward pass”:


The “Backward Pass”

Rule: The latest date for an event is the latest start date for all activities commencing from that event. Where common commencement from an even is present, the earliest of the latest start dates is taken.

Latest finish date for H, G = their earliest finish date = 13. If duration of H = 2 weeks, then latest date for event 4 is

latest date for event 6 – duration of H (i.e. 13-2) = 11. While the latest date for event 5 is latest for 6 – duration of G (i.e. 13-3) = 10.

The latest for event 3 is the latest of (11-4) and (10-3), both giving the value 7.

And so on, simply subtracting the duration of an activity from the latest date of the event it terminates at, for every path through the network (hence “backward pass”)


Resulting from the “Backward Pass”

1

?00

2

?86

3

?74

4

?119

6

?1313

5

?1010

A=6

B=4

C=3

D=4

E=3

F=10

G=3

H=2

This is the resulting diagram from a “backward pass”:


Calculating “Slack” (aka “Float”)

Rule: “Slack” is the difference between the earliest and the latest start/finish dates of an event.

This is the resulting diagram with “slack” included:

1

000

2

286

3

374

4

2119

6

01313

5

01010

A=6

B=4

C=3

D=4

E=3

F=10

G=3

H=2


The “Critical Path”

This is the longest time to project termination. The path through the PERT chart (activity network) that has no slack. Therefore…

1

000

2

286

3

374

4

2119

6

01313

5

01010

A=6

B=4

C=3

D=4

E=3

F=10

G=3

H=2


AON Diagrams

Diagram components (symbols) Nodes (drawn as circles or squares) Links (drawn as directed arcs)

Symbol meanings Nodes: Activities with specific durations Links: Precedence (sequencing)

These diagrams are not included in your (BCIS) syllabus. Feel free to research them individually for better background.


Project Planning Diagrams

You should have already discussed this type of chart in earlier courses, so I will be very brief.

Bar charts (aka Gantt charts) can be put to multiple uses. However in s/w development they are mainly used for… Staff allocation

Who does what Activity schedule

When activities begin and end (activity extent)


Gantt Chart Example

1

000

2

286

3

374

4

2119

6

01313

5

01010

A=6

B=4

C=3

D=4

E=3

F=10G=3

H=2

Time(weeks)

ABCD

EFGH

Activity

10 32 54 76 8 109 1211 13

Based on thisPERT chart:

Criticalpath


That’s it!

No more personal slides on scheduling tools

Documents

Project Scheduling Tools As part of CSA3040 © 2003, 2004 – Dr. Ernest Cachia