CSIT214
IT Project Management
Project schedule management
Project management framework
(review)
3Scheduling
‘Time is nature’s way of stopping everything
happening at once’
Having
 worked out a method of doing the project
 identified the tasks to be carried
 assessed the time needed to do each task
Now, need to allocate dates/times for the
start and end of each activity/task
4Defining activities
 A project is:
 Composed of a number of activities
 May start when at least one of its activities is ready to
start
 Completed when all its activities are completed
 A milestone is a significant event that normally has no
duration
 It often takes several activities and a lot of work to
complete a milestone
 They’re useful tools for setting schedule goals and
monitoring progress
 Examples: obtaining customer sign-off on key
documents or completion of specific products
5Defining activities (cont.)
 An activity
 Must have clearly defined start and end-points
 Must have a duration that can be forecasted
 May be dependent on other activities being
completed first (precedence networks)
6Identifying activities
 Activity-based approach:
 list all activities, sub-activities (sub-sub-
activities and so on) for the project (Work
Breakdown Structure).
 Product-based approach
 list the deliverable and intermediate products
of project – product breakdown structure
(PBS)
 Identify the order in which products have to be
created
 work out the activities needed to create the
products
7Hybrid approach
Estimating Activity Durations
 Duration includes the actual amount of
time worked on an activity plus elapsed
time
 Effort is the number of workdays or work
hours required to complete a task and
does not normally equal duration
 People doing the work should help create
estimates
 An expert should review them
9Activity networks
These help us to:
 Assess the feasibility of the planned
project completion date
 Identify when resources will need to be
deployed to activities
 Calculate when costs will be incurred
This helps the co-ordination and motivation
of the project team
Activity networks (cont.)
 Developing an activity network involves
evaluating the reasons for dependencies
and the different types of dependencies
 Mandatory dependencies: inherent in the
nature of the work being performed on a project,
sometimes referred to as hard logic
 Discretionary dependencies: defined by the
project team, sometimes referred to as soft logic.
and should be used with care since they may
limit later scheduling options
 External dependencies: involve relationships
between project and non-project activities
Activity networks (cont.)
 Network diagrams are the preferred
technique for showing activity sequencing
 Schematic display of the logical relationships
among, or sequencing of, project activities
 Two main formats are the arrow and
precedence diagramming methods
Activity networks (cont.)
 Arrow diagramming method (ADM) (i.e., activity-on-arrow
network diagrams)
 Activities are represented by arrows
 Nodes or circles are the starting and ending points of activities
 Precedence diagramming method (PDM)
 Network diagramming technique in which boxes represent
activities
 Types of dependencies or relationships between activities
 Finish-to-start
 Start-to-start
 Finish-to-finish
 Start-to-finish
Activity networks (cont.)
Activity networks (cont.)
Formulating a network planning model
Do A
Do C
Do B
Do D
 An (activity-on-node) network planning model (i.e. precedence
network) represents activities as nodes and their dependencies
as edges:
 Should have only 1 start node and 1 end node.
 Each node has a duration.
 Edges normally have no duration.
 Times move from left to right.
 Should not contain loops.
 Should not contain dangles.
16
Lagged activities
 where there is a fixed delay between
activities e.g. seven days notice has to
be given to users that a new release
has been signed off and is to be
installed
Acceptance
testing
Install new
release
7days
20 days 1day
17
Types of links between activities
 Finish to start
 Start to start/ Finish to finish
Software
development
Acceptance testing
Test prototype
Document
Amendments1 day
2 days
18
Start and finish times
 Earliest start (ES)
 Earliest finish (EF) = ES + duration
 Latest finish (LF) = latest date when a
task can be completed without affecting
project end
 Latest start (LS) = LF - duration
Earliest start
Latest start
Latest
finish
Earliest finish
activity
19
Example
 earliest start = day 5
 latest finish = day 30
 duration = 10 days
 earliest finish = ?
 latest start = ?
Float = LF - ES - duration
What is it in this case?
20
Notation
Activity label, activity description
DurationEarliest
start
Earliest
finish
Latest
start
Latest
finish
Float
21
Complete for the previous example
Pen and paper exercise
Activity Duration Precedents
A 6
B 4
C 3 A
D 4 B
E 3 B
F 10
G 3 E, F
H 2 C, D
Draw an activity network using precedence network
conventions for the project specified as below.
Critical Path Method (CPM)
 Network diagramming technique used to predict total project
duration
 Critical path: series of activities that determine the earliest time
by which the project can be completed
 The longest path through the network diagram and has the
least amount of slack or float; amount of time an activity may
be delayed without delaying a succeeding activity or the
project finish date
 Calculating the critical path
 Develop a good network diagram and add the duration estimates
for all activities on each path through the network diagram
 Longest path is the critical path
 If one or more of the activities on the critical path takes longer
than planned, the whole project schedule will slip unless the
project manager takes corrective action
Critical Path Method (cont.)
 There can be more than one critical path if
the lengths of two or more paths are the
same
 Project managers should closely monitor
performance of activities on the critical path to
avoid late project completion
 Critical path can change as the project
progresses
Using Critical Path Analysis to Make
Schedule Trade-Offs
 Free float
 Amount of time an activity can be delayed
without delaying the early start of any
immediately following activities
 Total float
 Amount of time an activity may be delayed
from its early start without delaying the
planned project finish date
 Forward pass
 Determines the early start and finish dates
 Backward pass
 Determines the late start and finish dates
26
Forward pass
 Start at beginning (Day 0) and work forward following chains.
 Earliest start date for the current activity = earliest finish date
for the previous
 When there is more than one previous activity, take the latest
earliest finish
EF = day 7
EF = day10
ES = day10
27
Pen and paper exercise
Fill in the earliest start and earliest finish dates for each activity
28
Forward pass
Example
0
0
0
6
4
6
10
9
9
10
11
1374
84
29
Backward pass
 Start from the last activity
 Latest finish (LF) for last activity = earliest
finish (EF)
 Work backwards
 Latest finish for current activity = Latest
start for the following
 More than one following activity - take the
earliest LS
 Latest start (LS) = LF for activity - duration
30
Pen and paper exercise
Fill in the latest start and latest finish dates for each activity
SPM (5e) Activity planning©
The McGraw-Hill Companies,
2009
31
Float
Float = Latest finish - Earliest start - Duration
ES
Latest start
activity
LF
FLOAT
Earliest finish
32
Pen and paper exercise
Fill in the float for each activity
107
33
Critical path
 Note the path through network with
zero floats
 Critical path: any delay in an activity on
this path will delay whole project
 Can there be more than one critical
path?
 Can there be no critical path?
 Sub-critical paths
Critical path
Example

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