7.8.1 - property() function - version property

In 7.8.1 reference is made to the version property. The example code seems to 
illustrate a situation where the value of the version property is contained 
in the instance data.

This seems to me to be a very odd design. Why, for example, is there not a 
version attribute on the xforms:model element with, for version 1.0, the only 
legal value specified as "1.0"? Then an XForms processor knows what it is 
dealing with - at least as far as the XForms model goes.

I appreciate that a missing version attribute might by default be interpreted 
as "1.0" but why not put a version attribute on xforms:model and give it a 
value?

Andrew Watt