I've also had difficulties writing my own grammar files.
I opened a grammar support ticket at the end of March that has gone no where.
I've also noticed the doc is dated and incomplete. Please reply here if you find newer or more complete doc.
It's a shame, because grammar seems like it could be very powerful. But with out of date doc, and poor support, you can't really use it for anything other that the grammar files that come with the product.
For things like extended objects it is often worth formating the output of the command using tools like sed or awk so you can use one of the out-the-box grammers.
Not so useful for grammer files though.
I agree that we need an up-to-date grammer document.
Do you have the support call ticket id?