Mutually Exclusive Relationships

In some situations, relationships may be mutually exclusive, i.e. either one or other relationship may be present, but not both. For example, a particular HOME LEAVE may only relate to either a WARD or, if the PATIENT is not in a hospital, an ORGANISATION SITE, such as a care home, but not both as the patient can only be in one place from which the HOME LEAVE is taken. This 'either/or' situation is shown by a line spanning the relationships in question.

An example of mutually exclusive relationships in diagrams is given below: