Issue 17820: LiteralNull semantics (uml25-ftf)
Source: Nomos Software (Dr. Edward Willink, ed(at)willink.me.uk)
Nature: Revision
Severity: Significant
Summary: This makes no sense to me. The absence of a value is modeled by the absence of a value, particularly given that UML provides no CollectionTypes to model the multiplicity of values.If the upper bound is one, then LiteralNull could possibly be an alternative to a Literal'NotNull', but it isn't an empty set. If the upper bound is greater than one, how are any of the values really represented in UML?If LiteralNull is to be an optional value, it should derive from LiteralBoolean, LiteralReal. etc.

Suggest delete LiteralNull or redefine it solely for use as the '0' of a [0..1] multiplicity.

Resolution: 
Revised Text: 
Actions taken:
September 26, 2012: received issue
Discussion: 

End of Annotations:=====
s is issue # 17820

Problem: 8.004

Severity: Medium
Type: Structural
Location: 8.2.3 LiteralNull semantics p. 76
Title: LiteralNull semantics
Description:
This makes no sense to me. The absence of a value is modeled by the absence of a value, particularly given that UML provides no CollectionTypes to model the multiplicity of values.If the upper bound is one, then LiteralNull could possibly be an alternative to a Literal'NotNull', but it isn't an empty set. If the upper bound is greater than one, how are any of the values really represented in UML?If LiteralNull is to be an optional value, it should derive from LiteralBoolean, LiteralReal. etc.
 
Suggest delete LiteralNull or redefine it solely for use as the '0' of a [0..1] multiplicity.
 
Source: Edward Willink