Error in Semantic Interpretation Spec?

I looked through my archive of this group but did not find any reference
to this point so I hope I'm not bringing up an old issue
 
In Section 8  - Xml Example
 
There are several reference to an id property on the <ruleref> tag
according to the grammar spec this does not exist but the url and alias
do,
Which is correct?
 
Thanks
 
Nick Alexander
 
TranXactive Operations