Definition:Critical Path Analysis/Network
Definition
A CPA network is a diagram in the form of a network used in critical path analysis.
Its construction requires a precedence table.
There are two main types of CPA network, as follows:
Edges as Activities
A CPA network with edges as activities is a CPA network such that:
- the nodes model the start and end times of the activities
- the edges model the activities themselves.
The activities and their times for completion are used to label the edges.
The earliest possible end time for an activity is used to label the node representing the end time of that activity.
It is sometimes necessary to include dummy activities to link paths where common activities appear, but in general the paths are independent.
Nodes as Activities
A CPA network with nodes as activities is a CPA network such that:
- the nodes model the activities
- an arc from node $X$ to node $Y$ indicates that $Y$ cannot start until $X$ is completed.
Such arcs are labeled with the time taken for $X$ to complete.
There may be more than one such activity $Y$, in which case the arcs all bear the same time.
Comparison
A CPA network with edges as activities may require one or more dummy activities which are required to ensure the precedences are observed.
While this is viewed as a complication, each activity appears on only one edge.
Hence the sequence of activities is easier to follow than for a CPA network with nodes as activities.
On the other hand, a CPA network with nodes as activities does not require dummy activities to be implemented, but the same activity needs to be represented by more than one edge when more than one activity depends upon it.
Hence the sequence of activities is less easy to follow than for a CPA network with edges as activities.
Also known as
A CPA network is also known as an activity network.
Also see
- Results about CPA networks can be found here.