SQLI_DOMAIN (1.5212)    FILE (1)

The set from which all objects of that domain must be drawn.
The PRIMARY_KEY data type and domain is unique to SQLI. It is used to
relate primary keys to foreign keys unambiguously (see SQLI_TABLE_ELEMENT)
In SQLI, all table elements (SQLI_TABLE_ELEMENT) have a domain which
restricts them to their domain set. For each data type there is a domain
of the same name, representing the same set. Other domains have different
set membership restrictions. 
 
Each domain has a data type, which determines the rules for comparing
values from different domains, and the operators which may be used on them.