Exclusive Arc Relationship

The following figure illustrates an example of the exclusive arc relationship. An exclusive arc is an arc across two or more relationship ends; you can read each exclusive arc relationship as follows:

Each [entity] must be [relationship name] either to only one [entity] 
OR [relationship name] to only one [entity]

For example, each Product Comparison must be to only one Product Internal or to only one Product External as shown in the following figure.