1Part A1
1. Introduction
Contemporary projects varying from putting a human onto the moon to constructing a residential shopping center are astoundingly sizable, costly and complex. Managing such projects to ensure on time delivery while within the budget limitation is not an easy task. The complication of such projects arises when there exists large interdependence of activities (Taylor 2012:17). Particularly, certain activity may have one or more predecessors, in which it requires completion of other activities upon initiating (ibid). In dealing with such projects consisting of substantial dependency relations, managers seek to determine the most effective method of graphical process representation.

This paper will first introduce the two forms of network diagram: Activity on the Arc and Activity on the Nodes. Following which, comparison and contrast based on their flexibility and effectiveness are carried out to determined the optimal method for project managers.

2. The Network Diagrams
The network diagram is a useful tool for graphical representation of precedence association between the activities in a project (Larson & Gray, 2011:158).

In an activity on the arc network diagram, an arrow is used to represent each activity, which is referred to as an arc (Anderson et. al, 2012:585). A circle called node is used to indicate the start and end of each activity (ibid). The node is often referred to in conjunction with the term event, which represents the finishing of the activity which result in a node (ibid). In an example, “modifying the machine” can be an activity. Upon completion of this activity, the event “machine modified” occurs. An example of activity on the arc network diagram can be shown in Figure 1 below where numbers refer to events while letters refer to activities. Dummy activity is used to accommodate more complicated relationship