XMI24 — logic for use of position attributes in 4.5.6 and 4.12.2 is not clear

The logic for use of position attributes in 4.5.6 and 4.12.2 is not clear. For example it states "The default, -1, indicates to add the replacing elements at the end of the target element." however the model allows many target elements which may be distributed throughout - so the explanation does not make sense. Furthermore it's not clear what the effect of a positive value would be e.g. "5". This applies to Add as well as Replace. Even the text 'at the end of the target element' is not precise. I suspect the intent is to allow elements to be added in the sequence of others owned by a containing element but this is not at all clear.
Position is for some reason defined as xsd:string in the XSD fragment - whereas it is declared as Integer in the XMI model.
Also the purpose/effect of nested Difference elements is not explained.

A further problem is that the example for Add in 12.2.4 does not make sense: there is no indication that the new Class should be related to the target via the ownedElement association: the addition should be represented as an ownedElement.

And the Replace element is generally problematic in being able to specify both an element to be replaced and a position. Given that the intent was not to change the ‘content’ at all it also seems to be incompatible with various XMI options (e.g. serializing metamodel properties as contained XML elements would not work).