Making Data Models Readable - High-Performance Web Databases: Design, Development, and Deployment - page 243

Exhibit 16-3. Oracle method cardinaltiy and optionality.

There is also a question of whether attributes must be shown,
and if so, how.

Attributes.

The tidiest model clearly is one in which attributes are not shown. If the
model is being presented to a group for the purpose of communicating the
basic nature of the entities and relationships, it is better to leave them off.
In your presentation of the model, describe enough of them to make clear
the meaning of each entity, but they do not have to be on the drawing. Add-
ing them as text inside the entity boxes does not have a serious impact on
the overall readability of the model, however (as long as there aren't too
many), so they can be included, if desired. Exhibit 6 shows this. Note that
in this example, the attributes themselves have been flagged as to whether

Exhibit 16-4. James Martin cardinality and optionality.