An influence diagram (ID) (also called a relevance diagram, decision diagram or a decision network) is a compact graphical representation of a decision situation.
In the diagram below, the weather condition has influence on the weather forecast. The weather forecast has an influence on selecting the vacation activity. Both the vacation activity and the weather condition influences the satisfaction level.

In project management Influence diagrams comes in handy while performing;
- Dependency determination of activities
- Activity sequencing
- Risk identification