Network Diagrams

The WBS allowed you to identify groups of activities that you need to accomplish in your project. However, the WBS does not show the dependencies or sequence between these activities. A network diagram will allow you to illustrate this. Once your network diagram is ready, only then can you realistically start determining your project’s schedule.

A Network Diagram is a visual representation of a project’s schedule. Well known complements to network diagrams include the PERT[7] and Gantt[8] charts. A network diagram in project management is useful for planning and tracking the project from beginning to finish. It represents a project’s critical path as well as the scope for the project.

A good network diagram will be a clear and concise graphic representation of a project.

There are two types of network diagrams: The Arrow Diagram and the Precedence diagram. The arrow diagram depicts nodes for events and arrows for activities. The precedence diagram depicts activities in the order they occur. If you work in IT you will most likely use the arrow diagram. 

‘A’ and ‘B’ each represents an event node. These event nodes refer to an instant when an activity is started or completed. An event node occurs only when all activities entering the node have been completed. The arrow represents the activity that takes place during the event. For example, if a task in a project were “research competition’s ad campaign,” then the event nodes would designate the start and finish of this activity whereas the arrow would designate the activity itself.

Using the arrow and node method, you can depict project dependencies. In the diagram, you see that Event C depends upon activities from Events A and B to be completed, and Event D depends upon Event C’s activities to be completed.

Dotted lines with arrows represent “dummy arrows.” Rather than depict a dependency between two items, these arrows depict a logical relationship. Dummy arrows have no duration. They do not depict an activity. Instead, they transfer logic from one event node to another.

Once the project is mapped out, you can write a key for the visual representation, listing the duration of events and activities. The network diagram will provide you and your project team with a full visual representation of your project.

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[7] Program Evaluation Review Technique, a methodology developed by the U.S. Navy in the 1950s to manage the Polaris submarine missile program. A similar methodology, the Critical Path Method (CPM) was developed for project management in the private sector at about the same time.

[8] A Gantt chart is a horizontal bar chart developed as a production control tool in 1917 by Henry L. Gantt, an American engineer and social scientist. Frequently used in project management, a Gantt chart provides a graphical illustration of a schedule that helps to plan, coordinate, and track specific tasks in a project.

PERT Chart

A PERT chart presents a graphic illustration of a project as a network diagram consisting of numbered nodes (either circles or rectangles) representing events, or milestones in the project linked by labeled vectors (directional lines) representing tasks in the project. The direction of the arrows on the lines indicates the sequence of tasks. In the diagram, for example, the tasks between nodes 1, 2, 4, 8, and 10 must be completed in sequence. These are called dependent or serial tasks. The tasks between nodes 1 and 2, and nodes 1 and 3 are not dependent on the completion of one to start the other and can be undertaken simultaneously. These tasks are called parallel or concurrent tasks. Tasks that must be completed in sequence but that don't require resources or completion time are considered to have event dependency. These are represented by dotted lines with arrows and are called dummy activities. For example, the dashed arrow linking nodes 6 and 9 indicates that the system must be configured before the user test can take place, but that the resources and time required to prepare for the user test (writing the user guides and user training) are on another path. Numbers on the opposite sides of the vectors indicate the time allotted for the task.

The PERT chart is sometimes preferred over the Gantt Chart, another popular project management charting method, because it clearly illustrates task dependencies. On the other hand, the PERT chart can be much more difficult to interpret, especially on complex projects. Frequently, project managers use both techniques.

Gantt Chart

A Gantt chart is a horizontal bar chart developed as a production control tool in 1917 by Henry L. Gantt, an American engineer and social scientist. Frequently used in project management, a Gantt chart provides a graphical illustration of a schedule that helps to plan, coordinate, and track specific tasks in a project.

Gantt charts may be simple versions created on graph paper or more complex automated versions created using project management applications such as Microsoft Project or Excel.

A Gantt chart is constructed with a horizontal axis representing the total time span of the project, broken down into increments (for example, days, weeks, or months) and a vertical axis representing the tasks that make up the project (for example, if the project is outfitting your computer with new software, the major tasks involved might be: conduct research, choose software, install software). Horizontal bars of varying lengths represent the sequences, timing, and time span for each task. Using the same example, you would put "conduct research" at the top of the vertical axis and draw a bar on the graph that represents the amount of time you expect to spend on the research, and then enter the other tasks below the first one and representative bars at the points in time when you expect to undertake them. The bar spans may overlap, as, for example, you may conduct research and choose software during the same time span. As the project progresses, secondary bars, arrowheads, or darkened bars may be added to indicate completed tasks, or the portions of tasks that have been completed. A vertical line is used to represent the report date.

Gantt charts give a clear illustration of project status, but one problem with them is that they don't indicate task dependencies - you cannot tell how one task falling behind schedule affects other tasks. The PERT chart, another popular project management charting method, is designed to do this. Automated Gantt charts store more information about tasks, such as the individuals assigned to specific tasks, and notes about the procedures. They also offer the benefit of being easy to change, which is helpful. Charts may be adjusted frequently to reflect the actual status of project tasks as, almost inevitably, they diverge from the original plan.

You have now learned how to flesh out the activities involved in a project, determine the sequence of the activities, and establish a schedule. You are now ready for the next step – determining the resources that you need to accomplish your project activities. Note that once you have determined the resources and their availability, you may need to review your project schedule (Gantt chart).

Critical Path Method (CPM)

Definition

Critical Path is the sequence of activities that must be completed on schedule for the entire project to be completed on schedule. This is the longest duration path through the work plan. The duration of the critical path determines the duration of the entire project. Each task/activity on the critical path is called a critical task. If a critical task is delayed by one day, then entire project will be delayed by one day (unless another critical task can be accelerated by one day).

The critical path may change from time to time as activities are completed ahead of or behind schedule. There may be more than one critical path depending on durations and work flow logic.

A related concept is the critical chain, which adds resource dependencies.

The Critical Path Method (CPM) is one of several related techniques for doing project planning. CPM is for projects that are made up of a number of individual "activities." If some of the activities require other activities to finish before they can start, then the project becomes a complex web of activities.

Critical Path Analysis is an effective and powerful method of assessing:

• What tasks must be carried out
• Where parallel activity can be performed
• The shortest time in which you can complete a project
• Resources needed to execute a project
• The sequence of activities, scheduling and timings involved
• Task priorities
• The most efficient way of shortening time on urgent projects
• How long your complex project will take to complete
• Which activities are "critical," meaning that they have to be done on time or else the whole project will take longer

If you put in information about the cost of each activity, and how much it costs to speed up each activity, CPM can help you figure out:

• whether you should try to speed up the project, and, if so,
• what is the least costly way to speed up the project.

An effective Critical Path Analysis can make the difference between success and failure on complex projects. It can be very useful for assessing the importance of problems faced during the implementation of the plan.

PERT is a variant of Critical Path Analysis that takes a more skeptical view of the time needed to complete each project stage.

Activities

An activity is a specific task. It gets something done. An activity can have these properties:

• names of any other activities that have to be completed before this one can start
• a projected normal time duration

If you want to do a speedup cost analysis, you also have to know these things about each activity:

• a cost to complete
• a shorter time to complete on a crash basis
• the higher cost of completing it on a crash basis

CPM analysis starts after you have figured out all the individual activities in your project.

Getting & Estimating Resources

Now that you have a better overview of the activities and schedule of your project, you have to determine the resources that you will need to execute the activities. You will need resources such as people, material and other supplies. For example, in a website design project you would typically need graphical designers and programmers, access to rooms to hold your meetings, software, computers, and so on.

People

Let’s begin with the most important resource – people. You will need to determine the skills required for accomplishing the activities of your project. After this phase, you need to match people to those skills. A good way to do this is to create a skills sheet that matches skills to activities. Also keep columns for the name of people, their start dates, their cost and the training they need to accomplish their tasks – this information can sometimes be obtained at the same time. Here is an example of a sheet that you can use to accomplish this:

WBS	Activity	Skills Needed	Name of Person	Skills Level	Deliverable	Effort Days	Start Date	End Date	Cost
2.1	Write marketing content	Marketing	JJC	Expert	Marketing content for website	10	May 07	May 20	9,500
2.2	Write HR content	HR	AFH	Intermediate	HR content for website	8	May 10	May 30	7,600
2.3	Edit all content	Document editing	KDM	Expert	Edited content for website	5	Apr 04	Apr 20	4,000

The above table goes beyond simply matching activities and skills – it also contains columns for the names of the people who will execute an activity, their skills level, the deliverable that they are expected to produce, the date on which they can start and finish, and their cost. Fill in these columns as soon as you can. Often the managers of the people that you need will be able to commit the availability of these people for your project. However, it is recommended that you always cross-check this information with your project team members, and pay particular attention to the following:

• Check up the availability of your project team members by taking into account their vacations, sick days and the other projects that they are already working on.
• Ask the functional managers of your project team members to assess the skill set of their people, and the effort days that will be required by them to accomplish the activities assigned to them (always cross-check the effort days with the person who will executing an activity).
• The functional managers should be able to tell you how much their people cost. The more detail you go into when estimating the costs, the more accurate your cost estimates will be. So be detailed when it comes to costs as this frequently becomes an issue later on in the project.

Nonperson Resources

You may also need to factor in the availability of nonperson resources such as supplies, equipment and facilities. To do this, create a nonperson availability sheet similar to the example below:

WBS	Activity	Resource Needed	Time in Hours	Date(s) Needed
4.1	Design brochure	- Computer - Color Printer	80	04 to 29 Apr
4.2	Brochure review meeting	- Meeting room with computer connected to projector	3	04 May
4.3	Make copies of draft brochure	- Color Photocopier	2	05 May

Now that you have an idea of your resource requirements and their availability, go back to your Gantt chart. You might need to re-adjust it in order to take into account your team members’ or other nonperson resources’ availability.