Some basic rules for developing network diagrams are:
Network Diagrams flow from left to right
An Activity cannot begin until all preceding connected activities have been completed
Arrows on Network Diagrams depict the precedence and flow of Activities. Arrows can cross over each other without any impact.
Each Activity should have a unique identification number
It is acceptable to leave gaps between Activity Identifiers such as: 1, 5, 10, 15. This makes it easier to add missing Activities at a later date without having to renumber the entire Network Diagram.
Activity Identifiers should be ascending numbers that are as simple as possible
Looping is not allowed
Conditional statements are not allowed – the network diagram is NOT a decision tree
Activities can only occur once on a Network Diagram. If they are to occur a second time, they should have a different name and new identifier.
Experience suggests that when there are multiple starts, a common start node can be used to indicate a clear project beginning on the network. Similarly, a single project end node can be used to indicate a clear ending
There are two main approaches for developing Network Diagrams:
AON – Activity-On-Node – uses a node to depict an Activity
AOA – Activity-On-Arrow – uses an arrow to depict an Activity