UML25 — Fixed-point issues with the definition of default values for literals

The definition of LiteralBoolean in the XMI for UML1.5 includes the following:

<packagedElement xmi:type="uml:Class" xmi:id="LiteralBoolean" name="LiteralBoolean">

<ownedAttribute xmi:type="uml:Property" xmi:id="LiteralBoolean-value" name="value" visibility="public">

<defaultValue xmi:type="uml:LiteralBoolean" xmi:id="LiteralBoolean-value-_defaultValue"/>

</ownedAttribute>

So the default value for value, which is correctly specified as false in the model, is specified by the absence of a value attribute as “the default value for LiteralBoolean::value” in the XMI. This is circular and ill-defined.

One issue is with the XMI specification. The rule that property values should not be serialized when they have their default value should not apply when those properties are being used to define default values for themselves. Another issue is with the UML xmi. This needs to serialize the value for the default value of literals, regardless of other considerations. In the case above, value=”false”.

Resolving Issue 18286 against XMI will make it valid to serialize the default value of the value property for
literals. For UML 2.5, we will serialize them. XMI 2.5 will be published at the same time as UML 2.5 and
UML 2.5 will be serialized as an instance of it.