Hi,

The description of derive tells: "... creates a new object with two
slots: parent, which points to the object derived from; and mirror ..."

In my opinion, creation of the slot mirror is not a requirement. It is
presumed inherited from *the-root-object*. In my draft implementation
that second slot is not created but inherited.

I think that it is better to not require  that second slot because it
saves memory. But, of course, an implementation could be allowed
to add that mirror slot.

I propose a description of derive looking like:

Return an object derived of the message recipient. This creates a new
object at least one slot, the pure getter slot named parent that returns
the parent object. An implementation is allowed to create a second pure
getter slot named mirror that return the mirror object of the created
object.

regards