Occasionally, it may be necessary to include more than one entity of the same name in a Vocabulary. This can be accomplished using Domains. Domains allow you to bundle one or more entities in a subset within the Vocabulary, thus you can reuse entity names as long as the entity names are unique within each Domain. Additional Domains, referred to as sub-Domains, can be defined within other Domains.

Select Vocabulary > Add Domain, or click from the Studio toolbar.

A new folder is listed in the Vocabulary tree. Assign it a name. The example in the following figure shows a Vocabulary with two Domains, US_Fleet and WW_Fleet:

Figure 1. Using domains in the Vocabulary>

Notice that the entity Aircraft appears in each Domain, using the same spelling and containing slightly different attributes (FAAnumber vs. ICAOnumber). Notice, too, that the association role names from FlightPlan to Aircraft were named manually to ensure uniqueness: one is now USaircraft and the other is WWaircraft.