An Interrelationship Digraph, or relations diagram, works best when dealing with a somewhat complex process or problem. Use the interrelationship digraph when you need to uncover the root causes of a problem, or when you need to identify areas where multiple problems converge (so-called â€œbottleneckâ€ areas). This is especially useful if you are planning to implement a new process, and want to be able to foresee how potential problems could interact to cause larger problems. It is also very useful when an existing process has encountered difficulties that cannot be solved in and of themselves. By using the relations diagram to find the root causes of the difficulties, you can fully eliminate the problems.