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ITPM L4: The project infrastructure and organisation /Project Scheduling …
ITPM L4: The project infrastructure and organisation
/Project Scheduling
WBS basics
Scheduling Terminology
Activity on Node (AON)
Critical Path Analysis
Gantt Charts
Learning objectives:
Understand principle scheduling definitions
Understand a Work Breakdown Structure
Appreciate the necessity to schedule
Explain Activity on Node (AON) diagrams
Prepare a schedule
Calculate a network and identify critical path
Draw a simple Gantt chart
Appreciate the benefits of using both AON and Gantt Charts
Intro:Project Management = People Management
Understand principle scheduling definitions
a. Scheduling
Definitions
Scheduling diagrams
-Networks
-Gantt Charts
Uses of a project schedule
b. Project Schedules
The time plan
Illustrating dependencies
Derived from a WBS
Is the basis for
-Resource planning
-S curve
-Critical Activities and Milestones
-Baseline for monitoring and control
Understand a Work Breakdown Structure
a. What is a Work Breakdown Structure (WBS)?
A decomposition of the work to be done in a project
Define the total scope
Capture specific tasks and deliverables that can then be
-Costed
-Time defined
-Resources identified/assigned
-Completion criteria identified
-Any dependencies
b. Key Elements of a WBS
Top level is based upon project objectives
Breaks down through levels of granularity
Remember to incorporate
-project deliverables
-handover/closing deliverables
Uses a verb and noun relationship
-Paint 3 walls
-Assemble unit
Lowest level items are work packages
Appreciate the necessity to schedule
a. From WBS to Schedule
What activities must be done before?
What activities can be done at the same time?
What activities are done next?
Put the following activities in order (see next slide)
Activities should only be sequential when they rely on each other
-E.g. you can’t boil the kettle until you have filled it with water
b. Example: make a cup of tea (efficiently)
Fill kettle
Take mug from cupboard
Get tea bag from cupboard
Put tea bag in mug
Get milk from fridge
Switch kettle on
Wait for kettle to boil
Add water to mug
Wait for tea to brew
Remove tea bag
Add milk
Drink tea
c. Example solution
d. Preparing to schedule
e. Exercise: make a cup of tea (efficiently)
How long does it take (duration in seconds)?
Fill kettle (5)
Take mug from cupboard (3)
Get tea bag from cupboard (3)
Put tea bag in mug (2)
Get milk from fridge (10)
Switch kettle on (1)
Wait for kettle to boil (120)
Add water to mug (3)
Wait for tea to brew (90)
Remove tea bag (5)
Add milk (3)
Drink tea (300)
4.Explain Activity on Node (AON) diagrams
a. Definitions
Activities: take time and use resources
Network: graphical presentation of interdependent activities
Path: route between two or more events
Critical: if delayed will delay the project
Critical Path: sequence of Critical Activities
Near Critical Path: sequence of ‘almost’ critical activities
Milestone: important/significant event.
b. Networks
i. A visual representation of a project showing
nterdependencies of Activities
Milestones and dates
Critical path
Float for each Activity
ii. A Network facilitates
Coordination of resources
Optimisation of sequence
Estimation of schedule risk
c. Activity on Node (AON) Networks
AON Example
Microsoft Project Network View
Symbols can be altered to suit conventions
:
Project activities, dependencies, durations
Elements needed are:
Task ID, predecessors, Duration (days)
a. Project Duration- Forward pass
To calculate the Project Duration
Draw the network
Indicate dependencies
Link to start and end milestones
Work methodically forward through the network calculating Earliest Start and Earliest Finish Times for each Activity
Note the EST is the latest EFT of its predecessors (taking any precedence definitions into account)
Work in relative, rather than calendar dates
Draw the network example in the slides
Prepare a schedule
Using Software Tools for Scheduling
Advantages
Speed
Easy to update
‘What if’ modelling
Accuracy
Consistency
Tailor calendar
Different outputs for different stakeholders
Multi-user on a server
Interface with organisation’s systems
Limitations
Risk of over planning
Can’t take quality into account
Not managerial judgement
Becomes a fact, unchangeable, even if inaccurate
Can limit flexibility through conformance
GIGO : only as good as available data
b. Use of Lag
c. Schedule Reduction
Why go faster?
Market advantage
Contract incentive
Avoidance of late-delivery penalties
High speed operations: “crashing”
Usually adds to cost
Not all tasks may have a crash option
Different methods of work
Planned duration of projects can be reduced by selecting tasks to be crashed …
Schedule Crashing – Worked Example on lecture slide
Critical path activities
Schedule reduction- Formula on lecture slide
Crashing option
Other Considerations
Crashing must focus on the CP
Day-to-day or ‘block’ crash time
CP can change with crashing
It is possible to have multiple CPs in a complex project
Crashing must consider the task/deliverable and resource constraints
Crashing – A Summary
Set a target for schedule reduction
Calculate cost/time slope for all critical path Activities
Include Activities that become critical if critical path is all Crashed
Then
-either Crash Activities in order of increasing cost/time slope until the target is reached
-or Crash all Activities and then relax them in order of decreasing cost/time slope until target is just reached.
Calculate a network and identify critical path
b. What are we trying to work out?
i. Task and Project Duration
Earliest Start Time (EST)
Earliest Finish Time (EST + Duration))
a. Project Duration - Forward Pass
To calculate the Project Duration:
work methodically forward through the network calculating Earliest Start and Earliest Finish Times for each Activity
Note the EST is the latest EFT of its predecessors (taking any precedence definitions into account )
work in relative, rather than calendar dates
Examples on the lecture slide
b. Backward pass
To calculate the Latest Start and Latest Finish Times
Work from the final Activity/Milestone, backwards through the network
The Latest Finish Time of the Last Activity is set to the EFT previously calculated
LST= LFT - duration
Where a Activity has more than one successor, the LFT is the lesser of the successors LSTs
Example on the lecture slide
ii. Floats (spare time)
Latest Start Time (LST)
Latest Finish Time (LST + Duration)
a. Calculate Float
Total Float is the amount of time an activity can be delayed without affecting the project completion date
It is the difference between the latest and earliest start times : LST -EST
- The Total Float can be either:
LST-EST
or
LFT-EFT
Calculate Floats - Free Float
Free float is the amount of time an activity can be delayed without affecting the start date of any of its successors
Free Float = EST of earliest successor -EFT
Diagram on the lecture slide:
Free Float is the difference, EST (Successor) - EFT between the next early start and early Finish
Practice question: Nimbus 2000 Project on the lecture slide
iii. Critical path
where the Earliest and Latest Times are the same
Draw a simple Gantt chart
Network Example as a Gantt
Calendar view of the schedule
Scheduling software: Change the View on the toolbar
Pros Gantt:
Easy to read overview
Easy to construct
Interdependencies
Resource bar charts
Progress tracking
Cons Gantt:
Interdependencies unclear
Visually unclear
Gantt Using Project Software
Appreciate the benefits of using both AON and Gantt Charts
9. Closing thoughts
Scheduling is a key part of project planning
Ideally schedule as a core team, not alone
The schedule is our best guess of progress
The WBS is ESSENTIAL to project planning
The quality of WBS affects the detail of the schedule
Crashing must focus on the CP and near CPs
The arithmetic is easy; and typically done by scheduling software
The value is in interpreting the schedule and adjusting as we learn more about the project
