UML25 — IsNull not Boolean

IsNull not Boolean

Presumably this issue is about the isNull operation of ValueSpecification. The definition of the operation is “The query
isNull() returns true when it can be computed that the value is null.” The implication is that isNull returns true only if
“it can be computed that the value is null”. In other cases, it always returns false. So the return multiplicity is correct.
In any case, in practice this operation is overridden by subclasses of ValueSpecification in specific cases in which it
can be computed (e.g., LiteralNull::isNull returns true).
Disposition: Closed - No Change