Building the Analysis Model › Refining the Model › Handling Unusual Situations › Solitary Entities

Solitary Entities

An entity that is the only occurrence of its entity type is called a solitary entity.

The existence of solitary entities often indicates incorrect analysis of some kind. Evaluate solitary entities carefully.

For example, a model that depends on there being only one occurrence of some entity type, say factory, is time dependent. If more factories are added in the future, the model will require modification.

In other cases, where there is and will be only one occurrence of an entity type, ensure it is not a special instance of another, more general entity type. For example, an entity type representing the entire corporation has only one occurrence, and so might well fit into an entity type called organizational unit.