UMLR — Parameter types required for operation parameters

Operation parameters point to 9.4.4 notation. The BNF there requires a parameter to include the ':' and <type-expression>.

In practice, the tools do not require the display of the parameter type.

Now, I understand that the <type-expression> could be blank, because we don't say what a type-expression requires. I think this interpretation is not reasonable, the features of BNF should be used to explicility allow this field to be omitted. In addition, the ':' should not be required if the type is omitted.

Replace
<parameter name> ':' <type-expression>
with
<parameter name> [':' <type-expression>]