XMI24 — XMI does not allow the differentiation between "set to default" and "unset" states for properties

Tthe XMI spec clause 6.5.2 says:

"Properties whose values are the default values are not serialized. "

This contradicts the MOF spec, which differentiates between the "set to default" and "unset" states of Properties.

A possible resolution is to change the statement to rather say:

"Property values are serialized when their values are expliclity set (i.e. calling isSet() returns true) and not serialized otherwise."

After much discussion the proposal is to clarify the MOF spec such that there will be no distinction between the default value having been implicitly set (on creation) or explicitly set. In other words, there is no need to track and persist the explicit ‘set’ action. And default values are not serialized in either case.

On a related point, XMI allows the serialization of a property with a nil value to indicate ‘that it is empty e.g. <property1 xsi:nil=”true”/>. Also an empty element may be used. Both of these require that an XML element be used for the Property.
However this should be made clearer and the rule for this in 2b is incorrect in using xmiName not “xsi” and not allowing empty elements.
We should also clarify when the xsi declaration is needed.