UNIT-DECL ::= unit-decl UNIT-NAME UNIT-SPEC UNIT-IMPORTS UNIT-IMPORTS ::= unit-imports UNIT-TERM* UNIT-NAME ::= SIMPLE-ID
A unit declaration UNIT-DECL is written:
UN : US given UT1,...,UTnWhen the list UNIT-TERM* of unit terms is empty, it is simply written:
UN : US
It provides not only a unit specification US but also a unit name UN, which is used for referring to the unit in subsequent unit expressions, so that the same unit may be used more than once in a composition. In addition, the UNIT-IMPORTS lists any units UT1, ...,UTn that are imported for the implementation of the declared unit (corresponding to implementing a generic unit function and applying it only once, to the imported units).