Jane Doe & Jane Doe

Oct, 2012

BPP 3213 PROJECT ESTIMATION AND SCHEDULING

Lecture 2 Network Scheduling and Precedence Diagram Method (PDM)

Faculty of TechnologyUniversiti Malaysia Pahang

RECAP

Project life cycle

Organization Structure

Challenges

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)

Scheduling is for everyoneit 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.

The History

Brief History

Gantt Charts / Bar Charts

History Advantage Drawback

Until 1958, the only tool for project scheduling was a bar chart

Henry Gantt had developed a complete notational system showing progress with bar chart, thus they called Gantt charts

Simple to construct and read

difficult to determine the impact of slip on one task on the rest of the project

Brief History (cont’d)

Arrow Diagrams

History Advantage Drawback

Late 1950s and early 1960s, two methods of scheduling were developed to capture the sequential and parallel relationships among project activities

An arrow diagram help the team understand the interdependencies of the tasks

Tend to be too complicated for some teams

Brief History (cont’d)

Critical Path Method (CPM)History Advantages Drawbacks

Developed by Du Pont in 1957

Initially to address the challenge of shutting down chemical plants for maintenance and restarting it again once maintenance completed

Utilizes the planner’s knowledge, experience, and instincts in a logical way

Graphical view of the project

Predicts the time required for the project

Shows which activities are critical to maintain the schedule and which are not

CPM can be complicated, and complexity increases for larger projects

Does not handling the scheduling of personnel and resource allocation

Not always clear and need to be calculated carefully

Estimating activity completion times can be difficult

Brief History (cont’d)

Program Evaluation and Review Technique (PERT)

History Advantages Drawbacks

Developed by US Navy and Booze, Allen and Hamilton at late 1950’s

It allows for randomness in activity completion times

Has potential of reducing both time and cost required to complete the project

Complicated chart

Prediction inaccuracies

Brief History (cont’d)

Purpose of a Schedule

Purpose of Schedule

• Schedules are tool to :

Communicate time plan

Assess time plan

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

Schedule Development Process

Resource capacity

Resource capability

Estimates - times

Network-logic

Scheduling Project Schedule

Example Gantt Chart

Logic Diagram & Networks

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

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

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

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

start finishactivity

The Critical Path

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

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

What is CPM really?

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

The Critical Path (cont’d)

• Essentially, to construct a model for a project, we need:

WBS Time (duration) Dependencies

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

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

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

Precedence Diagram Method (PDM) (cont’d)

•Types of Dependencies:

- Finish to Start (FS) : the predecessor must be completed before the successor can start

Predecessor10 days

Successor5 days

FS

Start Day: 1Finish Day: 10

Start Day: 10 Finish Day: Start Day + 5

•Types of Dependencies:

- Start to Start (SS) : the successor can start at the earliest after the start of its immediate predecessor

Precedence Diagram Method (PDM) (cont’d)

Predecessor10 days

Successor5 days

SS

Start Day: 1Finish Day: 10

Start Day: 1Finish Day: 5 days after start day

•Types of Dependencies:

-Finish-Finish (FF): the successor will finish at the latest after its predecessor finished

Precedence Diagram Method (PDM) (cont’d)

Predecessor10 days

Successor5 days

FF

Start Day: 1Finish Day: 10

Finish Day: 10Start Day: 5 days before finish day

•Types of Dependencies:

-Start-Finish (SF) : the successor can finish only after the predecessor has started

Predecessor10 days

Successor 5 days

SF

Precedence Diagram Method (PDM) (cont’d)

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

15Activity A

15Activity B

SS =5

FF=10

• B must be finished not later than 10 days after A is finished and starts after 5 days A started i.e. starts at day 10

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

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

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

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

Summary

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

Questions??? He who ask is a fool for five minutes, but he who

does not ask is a fool forever.