add handover action to tables demo domain

[marcvinci]

• added handover action to domain
• added fluent for handover action to track, which items where already handed over. This fluent is removed again if an item is perceived on a table or in a box. This allows the handover action to be performed again if the item reappears in the scene.
• moved target_location parameter from class constructor to run() function

[alexander-sung]

If an item is perceived, is it considered as not (yet) offered? So I understand the changes to perceive() in tables_demo_api.py.

Edit: It's also in your description. ^^ However, this could cause problems if an offered item is perceived again "unintentionally", don't you think?

[alexander-sung]

About the item having been offered, I actually have no better idea for the general case because it really depends on the situation.

For the InCoRAP use-case, would it make sense not to discard the item_offered fluent on pick or perceive but instead treat it as a separate, explicit action?

[alexander-sung]

Although, it probably does not look as nice, I'd like to change the wording for the verb "to hand over" in contrast to the "handover" noun. There were inconsistencies before, so this is an opportunity to resolve them.

Other than the points addressed before, the demos also run well on my side.

[marcvinci]

However, this could cause problems if an offered item is perceived again "unintentionally", don't you think?

Yes, this will be the case if the offered item is placed again on one of the tables or inside a box. At least the item cannot be perceived unintentionally in the persons hand, since it uses the "on" and "in" facts to remove the item_offered fact.

For the InCoRAP use-case, would it make sense not to discard the item_offered fluent on pick or perceive but instead treat it as a separate, explicit action?

Yes, for InCoRAP the handover action will probably only be executed once for each item, but my reasoning behind the removal of the fluent after perceiving or picking up, is to have a more general case, where we can hand items over to a person and if that item is requested again and also found again on a table, the action can be repeated.

[alexander-sung]

A good thought. I just think it's really hard to say what the more general case is. Hopefully nobody will wonder about the item _offered fluent being cleared again but indeed, the item in question would need to be placed into the scene again, that's true.

One more thought about discarding on pick: The planner won't be able to plan to pick up the item again for handover unless that is also reflected in the UP action, so you probably want to add self.pick_item.add_effect(self.item_offered(item), False) also for consistency, right?

Edit: Actually, no - still doesn't seem to be meaningful. Currently, I prefer to remove it from the pick action and leave it for perceive with the reasoning you provided. I'm still open for better solutions, though. Please also add the reasoning as comment if you want to keep it for perceive.