For ACTION-2087 - Write down his impmplementation's version of in-scope evaluation

All,

(The following is just one step for ACTION-2087, and not an actual proposal
yet.)

I found the message I was looking for from 2010:

   https://lists.w3.org/Archives/Public/public-forms/2010May/0008.html

It comes with an example:

    https://gist.github.com/orbeon/401939

The message had one reply from Alain, and a follow-up by myself:

    https://lists.w3.org/Archives/Public/public-forms/2010May/0009.html
    https://lists.w3.org/Archives/Public/public-forms/2010May/0012.html

That example and initial question had more to do with how `bind` would
interact with `model`.

However, in the ensuing meeting, we continued the discussion on how to
switch context when `model` is present:


https://lists.w3.org/Archives/Public/public-forms/2010May/att-0017/2010-05-19.html

I got an action item:

    Action 2010-05-19.1: Erik Bruchez to ask public-forms and www-forms
implementors - When you switch models, to what context do you switch? root
element or do you go back to the in-scope context? Please cite use cases
that support your decision.

That action item was never really completed and the purpose was to see what
implementors did and why.

-Erik