1. BPP 3213 PROJECT ESTIMATION AND
SCHEDULING
Lecture 2 Network Scheduling and Precedence Diagram
Method (PDM)
Oct, 2012
Faculty of Technology
Universiti Malaysia Pahang
Jane Doe & Jane Doe

2. RECAP
Organization
Structure
Challenges
Project
life cycle

3. Purpose of this lecture
To better understand:
• brief history of scheduling techniques
• network scheduling and logic diagrams
• the importance of Critical Path Method (CPM)
• the fundamental elements of precedence diagram
method (PDM)

4. Scheduling is for everyone
it is a discipline that is
performed by every person,
every day.
Scheduling is an application of special
knowledge or judgment of the
mathematical , physical, or engineering
sciences to the conception or
implementation of creative work.

5. The History

6. Brief History
Gantt Charts / Bar Charts
History Advantage Drawback
Until 1958, the only tool Simple to construct and difficult to determine the
for project scheduling read impact of slip on one task
was a bar chart on the rest of the project
Henry Gantt had
developed a complete
notational system
showing progress with
bar chart, thus they
called Gantt charts

7. Brief History (cont’d)
Arrow Diagrams
History Advantage Drawback
Late 1950s and early An arrow diagram Tend to be too
1960s, two methods help the team complicated for
of scheduling were understand the some teams
developed to interdependencies of
capture the the tasks
sequential and
parallel relationships
among project
activities

8. Brief History (cont’d)
Critical Path Method (CPM)
History Advantages Drawbacks
Developed by Du Pont in Graphical view of the CPM can be complicated,
1957 project and complexity increases for
larger projects
Initially to address the Predicts the time required
challenge of shutting down for the project Does not handling the
chemical plants for scheduling of personnel and
maintenance and restarting Shows which activities are resource allocation
it again once maintenance critical to maintain the
completed schedule and which are not Not always clear and need
to be calculated carefully
Utilizes the planner’s
knowledge, experience, and Estimating activity
instincts in a logical way completion times can be
difficult

9. Brief History (cont’d)
Program Evaluation and Review Technique
(PERT)
History Advantages Drawbacks
Developed by US Navy It allows for Complicated chart
and Booze, Allen and randomness in activity
Hamilton at late 1950’s completion times Prediction inaccuracies
Has potential of
reducing both time and
cost required to
complete the project

10. Brief History (cont’d)

11. Purpose of a
Schedule

12. Purpose of Schedule
• Schedules are tool to :
Communicate time Assess time plan
plan

13. Purpose of Schedule (cont’d)
Benefits:
- Identify the timeframe
- Identify the resource requirement
- identify the key milestones
- Identify the key stakeholder engagement
points
- Assess impact of resource constraints
- Determine your commitment and obstacles

14. Schedule Development Process
Network-logic
Estimates - times
Project
Scheduling Schedule
Resource capability
Resource capacity

15. Example Gantt Chart

16. Logic Diagram &
Networks

17. Your New Tool
•Defacto standard for scheduling software in
construction industry has been Primavera Project
Planner aka P3
•In 2000, P3 has improved for the use by
manufacturing and IT industries

18. Your New Tool (cont’d)
•Major differences that distinguish one software
system from another are
•Ease of input
•Ease and variety of means of reporting output
•Features that permit the user to get around some
of the limitation of the math upon which CPM is
founded to more perfectly model the real world

19. Logic Diagrams and Networks
• Effective project plan – address equally the
parameters and activity logic
• Illustrate the inductive and deductive reasoning to
achieve objectives within time given
• Constructed similarly to bar charts – supposing
nothing will go wrong
• Normally accompanied by detailed
questions/checklist

20. The Logic of the Logic Diagrams
• backbone of traditional implementation of CPM is
graphical model of a project
•Basic component is the arrow
•Each arrow represents one activity in a project
activity
start finish

21. The Critical Path

22. The Critical Path
• The longest path throughout a project
network
• Has no slack (or float) therefore all activities
on the critical path must be completed as
scheduled
• End date will begin to slip – one day for each
day a critical activity is delayed

23. The Critical Path (cont’d)
• Originally, the critical path considered only
logical dependencies between terminal
elements
•Since then, it has been expanded to allow for
the inclusion of resources related to each
activity , through processes called activity-based
resource assignments and resource leveling

24. What is CPM really?

25. The Critical Path (cont’d)
• Also known as Critical Path Analysis (CPA) – is a
mathematically base algorithm for scheduling a set of
project activities
• An important tool for effective project management
• Commonly used with all forms of projects including
construction, software development, research
projects, product development, engineering, and plant
maintenance among others

26. The Critical Path (cont’d)
• Essentially, to construct a model for a project,
we need:
WBS Time (duration) Dependencies

27. Terms you have to get used to...
• Event: equivalent to a milestone – indicate the start
and finish dates
• Activity: element of work that must be accomplished
• Duration: total time required
• Effort: amount of work actually performed within the
duration

28. Calender Scheduling
• Calendar unit:
- Time measurement for project schedule
- The smallest unit of time
- In hours, days, or weeks, years, months, shifts, even
in minutes
• Take into account for issues such as:
- For non-working time (weekend, holidays)
- Resource constraint
- Change risk
- Cash flow
- Logistics

29. Precedence Diagram Method (PDM)
• Visual representation technique
• Depicts the activities involved in a project
• Also known as Project Network Diagrams
• PDM helps:
- Communicate
- Identify missing activities
- Identify critical activities
- Create project schedule

30. Precedence Diagram Method (PDM) (cont’d)
•Types of Dependencies:
- Finish to Start (FS) : the predecessor must be
completed before the successor can start
Predecessor FS Successor
10 days 5 days
Start Day: 1 Start Day: 10
Finish Day: 10 Finish Day: Start Day + 5

31. Precedence Diagram Method (PDM) (cont’d)
•Types of Dependencies:
- Start to Start (SS) : the successor can start at the
earliest after the start of its immediate predecessor
Predecessor
10 days
SS
Successor
5 days
Start Day: 1 Start Day: 1
Finish Day: 10 Finish Day: 5 days after start day

32. Precedence Diagram Method (PDM) (cont’d)
•Types of Dependencies:
-Finish-Finish (FF): the successor will finish at the latest
after its predecessor finished
Predecessor
10 days
FF
Successor
5 days
Start Day: 1 Finish Day: 10
Finish Day: 10 Start Day: 5 days before finish day

33. Precedence Diagram Method (PDM) (cont’d)
•Types of Dependencies:
-Start-Finish (SF) : the successor can finish only after
the predecessor has started
Predecessor
10 days
SF
Successor
5 days

34. Precedence Diagram Method (PDM) (cont’d)
Multiple PDM Relationships:
• Two PDM dependencies/relationships can be used
together – combination
• Having both SS and FF relationships in one activity
SS =5
15 15 • B must be finished not later than 10
Activity A Activity B days after A is finished and starts
after 5 days A started i.e. starts at day
10
FF=10

35. Precedence Diagram Method (PDM) (cont’d)
Lag Time:
• It’s a technique
• Occurs when you add time to the start or finish of
predecessor task
• Causes a gap in timing
• E.g.: FS dependency with 5 days lag = the successor
cannot start until 5 days the predecessor has finished

36. Precedence Diagram Method (PDM) (cont’d)
Lead Time:
• It’s also a technique
• Created when you subtract time from the start or
finish of predecessor task
• Causes overlap between two tasks
• Allow acceleration of the successor activity
• E.g.: FS dependency with 5 days lead= the successor
can start 5 days before the predecessor has finished

37. Level of Detail
• Should never have too little nor too much detail
• Logical structure with appropriate level of detail is
the key to tracking throughout the project
• Contents information required to manage the project
– only that information
• Rule of thumb:
- 80 hour rule
- if it make sense

38. Conventional Assumptions
• Activity duration – scheduling done based on
expected or most likely time duration for each activity
• Contingency allowance for activity duration
• Availability of resources
• Schedules to have low cost or ideally lowest cost

39. Summary
•Network scheduling and PDM are techniques
to assist PM in scheduling – translating project
brief into time schedule

40. Questions??? 
He who ask is a fool for five minutes, but he who
does not ask is a fool forever.