Make it possible to OR slot values

[indam23]

Description of Problem:
Currently only one slot value can be given per slot_was_set step or condition. It would be useful to be able to "OR" slot values, i.e. list multiple options that all qualify for that step, especially with many-valued categorical slots.

Currently the only way around is either to create "meta slots" which reflect a certain grouping of slot values, or to create individual stories for each slot value, even when the steps in each one are identical otherwise. This can lead to an explosion in the number of stories with a many-valued categorical slot.

(Bigger scope: it would also be useful to be able to OR slot names e.g. either the first_name or the logged_in slot have a value, although I have seen less clear examples where this would be the best way to solve a problem. )

Overview of the Solution:
Allow listing multiple allowable values per slot in a story or rule slot_was_set step (see examples). If in a conversation the slot is set to any one of those values, the dialogue state should be considered to match the story/rule at that point.

Examples (if relevant):

For example, given this slot:

slots:
  account_type:
    type: categorical
    values:
       - free
       - standard
       - gold
       - premium

There could be cases where you want to group the values into free, and standard, gold, premium,
and other cases where each individual value gets its own variant on a story, or the values are grouped differently:

stories:
   story: greet a customer on a free plan
   steps: 
      - intent: greet
      - slot_was_set:
         - account_type: free
      - action: utter_greet_free_customer

   story: greet a customer on any paid plan
   steps: 
      - intent: greet
      - slot_was_set:
         - account_type: 
               - standard
               - gold
               - premium
      - action: utter_greet_paying_customer

   story: list options standard and free
   steps: 
      - intent: what_can_do
      - slot_was_set:
         - account_type: 
               - standard 
               - free
      - action: utter_standard_options

   story: list options gold and premium
   steps: 
      - intent: what_can_do
      - slot_was_set:
         - account_type: 
               - gold 
               - premium
      - action: utter_advanced_options

Blockers (if relevant):
None known

Definition of Done:

• determine if this is the best way to address the problem.
• verify solution with Research and CSE.
• Open implementation issue with solution detailed.

[kaustuk]

@melindaloubser1 is this issue open for community? I would like to contribute.

[indam23]

It's still under discussion, so I'm not sure (@TyDunn )

[TyDunn]

Hi @kaustuk. If you are interested in contributing this, could you please sketch out a plan for how you would go about doing it?

[kaustuk]

@TyDunn thanks for the reply. Sure I will come up with plan by this weekends.

[TyDunn]

@kaustuk Thanks! This will help us figure out if we feel this can be handled by the community 🚀

[desmarchris]

at least four customers (including one of the biggest) have asked for this now so bumping it up in CSE priority

[joejuzl]

closing in favour of #8933