The interrelationship digraphs are part of the seven project management tools under the Perform Quality Assurance. It is a quality management tool that encourages creative problem solving in complex scenarios that are intertwined with logical relationships. It simply shows the cause and effect of relationships thus helping analyze the link between different aspects of a complicated situation.
This particular project management tool encourages the team members to avoid thinking in a linear way. It also explores the relationships of different issues including controversial ones thus allowing key issues to come out naturally.
Interrelationship digraphs are used to understand the cause and effect of relationship especially when a complicated solution is being implemented by the project manager. This type of tool can also be generated only after generating another diagram such as the tree, fishbone and affinity diagrams.
To create this particular diagram, it is important to write a statement that defines the issue and should be explored. Team members need to brainstorm ideas and write them around the main issues. Once the ideas are placed on the issue, connecting ideas with one another using arrows is important to indicate their relationship.
This term is defined in the 5th edition of the PMBOK.