**6.2 Activity on the node (AON) diagramming**

AON or precedent diagramming was developed in the late 1960's specifically to "do away" with the dummy activity. In this form of diagramming, the arrow represents "precedence;" it simply identifies what activity must be completed before the next can begin, with the arrowhead representing direction of flow through the network. In precedent diagramming the arrow does not represent work accomplished. Instead, work is represented on the node of the network – and in this case the node is represented by a rectangle with the name of the activity within the rectangle. Other information may also be entered into the rectangular node, including early start, early finish, late start, late finish, duration, cost, etc. The IT industry has adopted precedent diagramming as its predominant form of network diagramming.

#### **6.3 Rules and accepted practices**

Network diagramming is a scheduling technique fundamental to the skills of any project manager. There are a few basic rules, or accepted practices, that apply to all network diagrams:


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activity.

**Figure 4.** *Estimation.*

*Project Management Concepts*

*DOI: http://dx.doi.org/10.5772/intechopen.93766*

of both the start and end nodes will be zero.

**6.4 Activity duration estimating**

therefore, can have dummies.

((P + 4 M + O)/6)

shown in **Figure 4**.

**6.5 Critical path method (CPM)**

4.In well-formatted network diagrams, arrows may proceed from the left to the right, they can proceed up, or they can proceed down on the paper. In the absence of arrows, one can assume that the activities proceed from left to right.

Every project has one, and only one, starting point; and one, and only one, ending point. This is easily accomplished in the AOA format, but it is an accepted practice that is frequently violated in AON networks. The way to correct this error in AON formats is to add two additional nodes, one labeled "start" and the other labeled end. Then, all of your initial activities are initiated from the start node and all of your hanging activities will be tied in to the end node. Of course, the duration

*PERT (Program Evaluation Review Technique)* has an emphasis on meeting schedules with flexibility on costs and it can be drawn only on an AOA diagram, and

2.PERT calculates an estimated time using the following equation:

1.Has 3 estimates per activity: Optimistic (O), Pessimistic (P), and Most likely (M)

3.These estimates can be used to describe a Beta Distribution. You are probably familiar with a Normal Distribution (similar to the shape of a Bell and used in Six Sigma Quality Management). A Beta Distribution has a different shape as

Notice how there is a long tail to this distribution making different than a normal distribution where the m would be an equal distance between the a and the b and would represent the 50/50 mark of a distribution (50% of sample times falls

Although this technique may use the words critical path, it does not refer to finding the critical path. It refers to estimating based on one time estimate per

to the left of m and 50% of sample times falls to the right of m).

*Operations Management - Emerging Trend in the Digital Era*

Of these, the network diagram shows interdependencies of all tasks and

Network diagrams have evolved as a de facto standard for building project schedules because of their emphasis is on activity dependencies. They depict entire projects, or subprojects, as visual maps that portray activities in their required order of execution. These diagrams can be developed in one of the following two

• Activity-on-Arrow (AOA), also called Activity-on-Line (AOL) or Arrow

• Activity-on-Node (AON) also called Precedence Diagram Method (PDM)

to the fact that additional memory is needed to program the dummy activities.

AOA diagramming is almost never seen today in popular software programs due

AON or precedent diagramming was developed in the late 1960's specifically to "do away" with the dummy activity. In this form of diagramming, the arrow represents "precedence;" it simply identifies what activity must be completed before the next can begin, with the arrowhead representing direction of flow through the network. In precedent diagramming the arrow does not represent work accomplished. Instead, work is represented on the node of the network – and in this case the node is represented by a rectangle with the name of the activity within the rectangle. Other information may also be entered into the rectangular node, including early start, early finish, late start, late finish, duration, cost, etc. The IT industry has adopted precedent diagramming as its predominant form of network diagramming.

Network diagramming is a scheduling technique fundamental to the skills of any project manager. There are a few basic rules, or accepted practices, that apply to all

1.An arrow is a straight line and the arrows showing precedence may have right angles built into them. Good practice requires that all such bent arrows be bent at right angles, and only at right angles, so that we can clearly identify that the

direction. There must be an arrowhead on each arrow to indicate its direction.

3.The arrows cross each other frequently – but when good practice is used these arrows will cross each other at right angles. The purpose of this is to help us

2.An arrow is always directional, with the arrowhead demonstrating the

follow the arrows without getting sidetracked onto another arrow.

illustrate the workflow of the project and assumes greater importance.

• Bar (Gantt) Charts

• Network Diagrams

**6.1 Network diagram**

Diagramming Method (ADM)

**6.2 Activity on the node (AON) diagramming**

**6.3 Rules and accepted practices**

bend was intended.

network diagrams:

forms:

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4.In well-formatted network diagrams, arrows may proceed from the left to the right, they can proceed up, or they can proceed down on the paper. In the absence of arrows, one can assume that the activities proceed from left to right.

Every project has one, and only one, starting point; and one, and only one, ending point. This is easily accomplished in the AOA format, but it is an accepted practice that is frequently violated in AON networks. The way to correct this error in AON formats is to add two additional nodes, one labeled "start" and the other labeled end. Then, all of your initial activities are initiated from the start node and all of your hanging activities will be tied in to the end node. Of course, the duration of both the start and end nodes will be zero.
