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Software Project Management
Notes 3. The …………………….. allows you to compute the earliest time at which the project can be
completed.
4. Even for large projects, the Network Planning Model gives a clear ………………….. picture
of the relationship between project activities.
8.2 Building the Network Diagram using the Precedence
Diagramming Method
It is also called as the Activity-on-the-Arrow (AOA) method (See figure 8.2). An arrow represents
each activity. The node at the left edge of the arrow is the “begin the activity,” while the node at
the right edge of the arrow is the “end the activity.” Every activity is represented by this
configuration. Nodes are numbered sequentially, and the sequential ordering had to be preserved,
at least in the early versions. Because of the limitations of the AOA method, ghost activities had
to be added to preserve network integrity.
Figure 8.2: The Activity-on-the-Arrow Method
Later on, the AOA method lost its appeal, and a new method known as the Activity-on-the-Node
(AON) method replaced it. The term more commonly used to describe this approach is Precedence
Diagramming Method (PDM) (see figure 8.3).
Figure 8.3: PDM Format of a Project Network Diagram
Each activity in the network diagram is represented by a rectangle that is called an activity node
(see Figure 8.4). The entries in the activity node describe the time-related properties of the
activity. Some of the entries describe characteristics of the activity, such as its expected duration
(E), while others describe calculated values (ES, EF, LS, LF) associated with that activity. These
terms will be defined later on in this unit.
In order to create the network diagram using the PDM, you need to determine the predecessors
and successors for each activity. Here, you are looking for the technical dependencies between
activities. Once an activity is complete, it will have produced an output, a deliverable, which
becomes input to its successor activities. Work on the successor activities requires only the
output from its predecessor activities.
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