Allowing the player to create models of anything in the game world; parsing the name "model [thing]" or even just "[thing]" to refer to these newly-created models; asking "which do you mean, the model [thing] or the actual [thing]" when there is ambiguity.

We rely here on the understanding-by-relations rules we've already learned, but there is an additional trick: we want to make sure that if the player types "original" or "actual", this word will not be taken to refer to the thing modeled:

"Originals"
A model is a kind of thing. 10 models are in the model-repository.
Appearance relates one thing to various models. The verb to be shown by means the appearance relation.
Indication relates a model (called X) to a thing (called Y) when Y is shown by X and Y is suitable.
Understand "actual" or "original" as "[actual]". Understand "[actual]" as something when the item described is not a model.
Definition: a thing is suitable:
   if the player's command includes "[actual]", no;
   yes.
Understand "[something related by indication]" as a model.
After printing the name of a model (called target): say " [random thing shown by the target]"

Now our duplication command – for the sake of simplicity, we'll suppose that in this scenario the player is duplicating objects by magic rather than creating them out of physical materials or supplies:

Understand "duplicate [something]" as duplicating. Duplicating is an action applying to one visible thing.
The duplicating action has an object called the selected model.
Setting action variables for duplicating:
   let N be a random model in the model-repository;
   now the selected model is N.
Check duplicating:
   if the selected model is nothing, say "You're out of power." instead.
Carry out duplicating:
   now the noun is shown by the selected model;
   move the selected model to the player.
Report duplicating:
   say "You concentrate and manifest [a selected model]."

Now, the challenge is that we want to print the word "actual" before printing the name of an object, but only during disambiguation questions and only when we are not printing the name of the object as part of a model-name! (If we are not careful about the latter point, we will get responses such as "Which do you mean, the model actual deer or the actual deer?" which of course defeats the whole purpose.

The way around this is to remember that activities stack: we're printing the name of the deer while printing the name of a model that involves the deer. So if we set a flag while printing the name of a model, we can control the way the deer's name prints during the transaction. (We could use our …while clause to specify while not printing the name of a model, except that we're already using it for "while asking which do you mean", and these do not stack.) So:

The virtual-context is a truth state that varies. The virtual-context is false.
Before printing the name of a model:
   now virtual-context is true.
After printing the name of a model:
   now virtual-context is false.
Before printing the name of something (called target) while asking which do you mean:
   if the target is not a model and virtual-context is false:
      say "actual ".
Forest is a room. It contains a deer and a daisy. The deer is an animal.
Test me with "duplicate deer / x model deer / x deer model / drop deer / x deer / actual / x deer / model".
Test me with "duplicate deer / x model deer / x deer model / drop deer / x deer / actual / x deer / model".
Forest
You can see a deer and a daisy here.

>(Testing.)

>[1] duplicate deer
You concentrate and manifest a model deer.

>[2] x model deer
You see nothing special about the model deer.

>[3] x deer model
You see nothing special about the model deer.

>[4] drop deer
(the model deer)
Dropped.

>[5] x deer
Which do you mean, the model deer or the actual deer?

>[6] actual
You see nothing special about the deer.

>[7] x deer
Which do you mean, the model deer or the actual deer?

>[8] model
You see nothing special about the model deer.