The Start To Finish Relationship

Published Date: 02 Nov 2017

Introduction

In this lecture we described the basics of the most common project management tools used. First we present GANTT charts. Secondly, we presented network diagrams. Thirdly, we presented CPM. Finally, we presented PERT analysis. For each tool we presented its definition, its graphical representation, its advantages and disadvantages. We also define the critical path of network diagrams, CPM and PERT.

Learning Outcomes

Be familiar with how Gantt Charts are used in project management and its advantages and disadvantages

Be familiar with how network diagrams are used in project management and its advantages and disadvantages

Be familiar with how critical path method and PERT are used in project management and their advantages and disadvantages

1.0 Introduction

Project planning, monitoring and control use project management tools to facilitate implementation of all project management tasks. These tools play a large role in all phases of a project. They will enable project managers to manage their projects successfully. Computer-Aided Software Engineering (CASE) tools can assist project managers and development teams in managing their projects.

Most project managers use the following tools to assist in the management of their projects: Network diagrams , CPM charts, Gantt charts, PERT analysis. Project managers use these tools to automate the process of creating project charts, network diagrams, calendars, resource lists and activity lists.

CASE allows for all personnel involved in a project to communicate effectively and recognise the current status of the project in terms of its progress. Personnel that benefit from the usage of CASE could be in the shape of project developers, designers, software testers and so on.

This lecture describes some tools that are used extensively in project management, such as GANTT charts, network diagrams, and PERT analysis.

2.0 Gantt Charts

A Gantt chart is used in the initial stage of the project to illustrate the various parts/tasks of the project that need to be carried out as well as the time taken for these tasks to be completed.

A basic Gantt chart does not display the dependency or relationships between the activities. Enhanced Gantt charts are capable to displaying time relationships and time dependency among tasks. The Gantt chart is usually used in combination with network diagrams (which show the dependency and relationship between project activities), the critical path method (CPM), and the project schedule to give a clear overall picture of the project.

Gantt Charts display the list of project tasks and related information and shows tasks and durations over time. It is used to enter and schedule a list of tasks.

A Gantt chart lists project activities on the left-hand side of the chart and the time line on bottom of the chart (See Figure 1 for an example). The Gantt chart could display project information at the left side while displaying this information on the right hand side as a chart. The left side of the display shows information such as listing tasks, when they start and finish and their duration as well as the needed resources associated with them. On the other side, this information is graphically represented using bars. The bar illustrates the initialization and completion of the task. Finally, the positioning of the surrounding bars establishes if a task has dependencies before it or if other tasks are dependent on it.

Month

Activity

Activity A

Activity B

Activity C

Activity D

Activity E

Feb2010

Mar2010

Apr2010

May2010

Jan2010

Jun2010

Jul2010

Figure 1: An example of a Gantt chart

Time granularity of the time line should be adjusted based on the duration of the project. For example, if the project estimated duration is one year, then a monthly timeline would be more suitable than a quarterly one. If the duration is a month, then a daily timeline is the most suitable.

Gantt chart has the following advantages:

It is simple

It is easy to understand

It is easy to create and maintain

Gantt chart has the following disadvantages:

It does not show relationships or interdependencies among project activities

There is no uncertainty of a given project activity (as does PERT)

The objectives of the Gantt Chart are:

Display project tasks and the amount of time each task will take.

Establish sequential dependencies between tasks through using relationships.

Assign personnel and other resources to tasks.

Show tasks progress over time. Project managers can track project progress by comparing planned and actual start and finish times and by seeing how much of the task has been completed.

View tasks graphically.

There are four relationships between activities where activities can relate to one another in a Gantt chart. They are as follows:

The first relationship is the "Finish to Start" where the start of an activity X depends on the finish of the another activity Y. This means that activity X can not start until activity Y completes. Figure 2 represents a finish to start relationship. Figure 2 shows the Finish to Start relationship.

Feb2010

Mar2010

Apr2010

May2010

Jan2010

Jun2010

Jul2010

S

Activity Y

Activity X

Month

Activity

F

F

S

Figure 2: the "Finish to Start" relationship

The second relationship is the "Finish to Finish" where the finish of an activity X coincides with the finish of the another activity Y. This means that activity X and activity Y complete at the same time. Figure 3 represents a finish to finish relationship.

Feb2010

Mar2010

Apr2010

May2010

Jan2010

Jun2010

Jul2010

Activity Y

Activity X

month

Activity

S

F

F

S

Figure 3: The "Finish to Finish" relationship

The third relationship is the "Start to Start" where the start of an activity X coincides with the start of the another activity Y. This means that activity X and activity Y start together at the same time. Figure 4 represents a finish to finish relationship.

Feb2010

Mar2010

Apr2010

May2010

Jan2010

Jun2010

Jul2010

Activity Y

Activity X

month

Activity

S

F

F

S

Figure 4: The "Start to Start" relationship

The fourth relationship is the "Start to Finish" where the start of an activity X coincides with the finish of the another activity Y. Figure 5 represents a finish to finish relationship.

Feb2010

Mar2010

Apr2010

May2010

Jan2010

Jun2010

Jul2010

Activity Y

Activity X

month

Activity

S

F

F

S

Figure 5: The Start to Finish relationship

The above is the description of a basic Gantt chart. Most Gantt charts are far more detailed and complex. Complex Gantt charts show relationships interlinking various tasks, what is called the "slack times" and the "absolute latest finish" times are also represented using different kinds of lines. Gantt charts can also illustrate landmarks or signposts which represent certain stages of the project. Interactive Gantt charts which are regularly updated can also show the current status of the project and give an indication of the progress that is being made. Due to Gantt charts becoming rather complicated, it is recommended that some sort of legend is created in order to make the reading/understanding of the Gantt charts a lot more straightforward.

Figure 6 shows an example of a complex Gantt chart (created by Microsoft Project 2000) clearly illustrating the amount of information and detail that can go into them.

The figure shows the resource names, the relationships between the various tasks as well as indicating the progress of the tasks in terms of completion. Milestones have been represented as red diamonds.

Complex Gantt chart.

Figure 6: An example of a detailed Gantt chart using Microsoft Project 2000

Gantt Charts can also show the expected, optimistic, or pessimistic time schedule scenarios.

A Gantt chart shows the baseline and scheduled Gantt bars for each task. Actual schedule of the project is compared with scheduled Gantt bars for each task that are shown in the Gantt chart.

3.0 Network Diagrams

The network diagram displays project tasks and task dependencies in a network or

flowchart format. A network diagram is similar to Gantt chart but it also shows all tasks and task dependencies. A basic Gantt chart does not display the dependency or relationships between the tasks/activities. Hence, a network diagram can be described as a visual representation of the tasks involved in the project. Network Diagrams were developed in the 1950’s.

The objectives of the network diagrams are to:

Create and fine-tune project schedule.

Show tasks interdependence and to specify the task sequence, as well as determine start and finish task dates.

Graphically show completed, in-progress, and not-yet-started tasks.

Assign personnel and other resources (such as equipment) to specific tasks.

Network Diagrams can be customized to view project tasks at different levels of abstraction. They can be viewed to fit needs of project managers. Project managers can customize network diagrams appearance or create new, customized versions.

An activity network is a labeled graph, with:

nodes corresponding to activities

arcs labeled with estimated times

activities are linked if there is a dependency between them.

Similar to CPM, network diagrams have two classic formats:

Activity on Arrow (AOA): In an AOA network diagram circles represent events such as ‘start’ or ‘end’ and lines represent tasks.

Activity on Node (AON): In an AON network diagram tasks are represented by nodes. Nodes can be circles or rectangles. Task information is written on the node. Arrows are dependencies between tasks.

Each task in the network diagram is labeled with

Identifier (usually a letter/code)

Duration (in standard unit like days)

A path is a chain of tasks that are connected to one another from the start of the project to the end of it. A network may have more than one path running at the same time.

A critical path in a network diagram is the specific set of sequential tasks (or even a single task) upon which the project completion date depends. That is, when the last task in the critical path is completed, the project is completed. If it is important for the project to finish on schedule, then project manager should pay close attention to the tasks on the critical path and the resources assigned to them. These elements determine whether the project will finish on time or not. The series of tasks are generally interrelated by task dependencies. Although there are likely to be many such networks of tasks throughout the project plan, the network finishing the latest is the project's critical path. A critical path is also called the longest full path.

Network diagrams advantages include the following:

Show task precedence well

Reveal interdependencies not shown in other techniques

They are able to calculate critical path

Network diagrams disadvantages include the following:

Default model assumes that resources are unlimited

Task dependencies need to be incorporated manually when determining the "real" Critical Path

They are difficult to follow on large projects

There are four steps in creating a network diagram. These steps are as follows:

Step 1: Identify the relationships between the tasks/ activities.

Step 2: Identify the milestones in the project. A milestone can be described as the part of a project when a task is complete and requires an evaluation of some sort, most commonly a summary of how the task was completed and resources used to complete it.

Step 3: Graphically represent the tasks/activities and milestones on a network diagram. The use of a ‘start project’ and ‘end project’ box at the start and end of a network diagram is commonly used, indicating the initializing and completion of the project.

Network diagrams usually start with a box called 'Start project' and end with a box called 'End project'

Step 4: Review the logical flow and order of the network and tasks sequence and dependence.

4.0 Critical Path Method (CPM)

Critical Path Method (CPM) is an analysis technique that is used to predict project duration. It helps in project management to define project overrun problems. The critical path method (CPM) is a technique that is used to illustrate the order of the tasks within the project, showing how each task is dependent on the one before it. This method uses nodes (circles) and links (arrows). There are two methods used to represent activities/tasks and events using CPM. These are:

Activity on Arrow (AOA) method. This method illustrates activities/tasks using arrows and events are represented by circles.

Activity on Node (AON) method. This method makes use of circles to represent activities and arrows are used to represent the priorities that are assigned to these activities.

Figure 7 shows an example of a CPM diagram using nodes and links.

1

2

3

4

5

6

Figure 7: An example of a CPM diagram

CPM uses critical path analysis technique to estimate project duration. It is a key tool used by project managers to help them plan and control their project which in turn eliminate the chances of the project overrunning. The critical path of a project is a sequence of tasks in the CPM diagram that establishes the quickest time a project can finish. This critical path is the longest path through the CPM network diagram. It established by combining the duration of the paths in order to work out the longest one.

5.0 Program Evaluation Review Technique (PERT)

Program Evaluation Review Technique (PERT) is a project time management technique that is used in projects that involve high ‘uncertainty’ levels in regards to specific tasks’ durations.

PERT uses duration ranges and the probability of an estimate falling to a given range. It also uses an expected value (or weighted average) to determine durations of activities.

PERT applies the critical path method (CPM) to a weighted average duration estimate of tasks/activities.

PERT makes use of time estimates that are based on probability. These estimate are as follows:

Optimistic estimate which is the estimate that would likely to occur 1 time in 20 times

Most likely estimate which is the estimate that modal value of the distribution

Pessimistic estimate which is the estimate that would be exceeded only one time in 20.

The average of the three above estimates is then calculated using a formula which will be discussed in the next section.

PERT uses a formula to calculate the expected durations of the activities. This formula is called the weighted average formula. These durations are then used as input to network diagram.

The following method is used to calculate the expected durations of the activities.

Start with 3 estimates: optimistic, most likely, and pessimistic.

Use the following PERT formula to estimate a task duration

te = (a+4m + b)/6

Where

te is the expected time

a is the optimistic time estimate

m is the most likely time estimate

b is the pessimistic time estimate

PERT advantages include the following:

Helpful when tasks durations have uncertainty

It tries to address the risk associated with duration estimates.

PERT disadvantages include the following:

It is time consuming

It has intensive work and calculations.

It assumes unlimited resources which is big issue

Lack of functional ownership of estimates

It is rarely used in practice where is usually used only for large and complex project

It requires several duration estimates

A PERT could be confused with network diagrams. A PERT chart is actually a normal network chart with PERT calculated task durations displayed.

A comparison between CPM and PERT show that:

Both CPM and PERT use Network Diagrams

CPM is deterministic while PERT is probabilistic

CPM uses only one estimate while PERT uses three estimates

PERT is rarely used

Summary

In this lecture we described the basics of the most common project management tools used. First we present GANTT charts. Secondly, we presented network diagrams. Thirdly, we presented CPM. Finally, we presented PERT analysis. For each tool we presented its definition, its graphical representation, its advantages and disadvantages. We also define the critical path of network diagrams, CPM and PERT.

Exercises

Explain how a Gantt chart can assist in the effort to deliver software on time.

Define a network diagram. What are its advantages and disadvantages?

Define a CPM tool. What are its advantages and disadvantages?

Define a PERT tool. What are its advantages and disadvantages?

Compare between a network diagram and a CPM tool.

Compare between a PERT tool and a CPM tool.

Define critical path and its importance.

Explain how a critical path can change during a project.

Why is it important to know the critical path?

How do you shorten the critical path?

Can there be multiple critical paths in network diagrams?

Can there be the critical path across multiple projects?

Tutorial/Practical

You can purchase project management CASE tools from any computer software store. The most commonly one you are likely to find is MS Project. Write a 5 page report on MS Project.

Do a search on the Web and see how many project management packages you can find. Then, write a 5 page report to compare and contrast these tools.

There is no single package that is best in all situations. Choose a package that suits complex project criteria and budget, that is easy to use, with good functionality, easy of reporting and charting the project. Then, write a 5 page report on that package.