On 03/07/2015 08:58, Ulrike Fischer wrote:
> - .default:X can imho be reset with .default:n= {}.
> - .groups:n can imho be reset with  .groups:n = {}.

As previously noted, I'll alter this behaviour for .groups:n so a blank
version means 'remove from grouping'. I'll also document that.

The .default:n is different: an empty default is not the same as no
default at all (as a default means effectively a value is always given).
I will though note exactly that point in the docs.

> -  the action can be reset by setting a new action.

True, and again I will clarify docs.

> Missing is ".value_not_required:" and ".value_not_forbidden:". 

I wonder if best would be to deprecate current .value_required: and
.value_forbidden: and go to .value_required:n and .value_forbidden:n
taking boolean values? Makes the syntax a little longer but is explicit
and so allows reversal. Alternatively, we could leave this as-is is
simply note that to clear it you need to 'remake' the key by undefining
it then re-declaring it. It's an unusual case so that might be as
sensible as changing the property now.

> Missing is an explicit ".unknown:", which would e.g. allow to remove
> choices from a key. An accompayning ".known:" which reactivates the
> key would be interesting too. (I don't know if the code allows
> this). 

As previously noted, making a key unknown removes the code behind it
entirely. Unless there is a compelling use case I'm minded to leave this.

> An additional ".delete:" which clears a key completly would be good
> too. 

Based on the fact that as far as possible the key property names follow
other expl3 things (see .tl_set:N, etc.) I will probably go with
.undefine:, although .unknown: would also fit nicely with the way keys
are described.

Unless there is further feedback I'll implement all of this over the
next couple of days and prepare a release to CTAN.
--
Joseph Wright