Add unfeaturized flag to slots

[wochinge]

Motivation

Slots themselves cause confusion in another way -- users may define the type based on what they hold (e.g. “text”) but not include them in their stories because they shouldn’t affect the flow -- it’s common that users don’t understand that setting the type to text will actually featurize the slot, leading to unpredictable behavior.

Suggested Solution

1. Add a flag unfeaturized: true / false to the configuration of each slot in the domain. Return the slots features in as_feature depending on the value of the unfeaturized flag

   slots:
     os:
       type: categorical
       values:
       - Windows
       - MacOS
       - Linux
       unfeaturized: true
    # this would previously been
    # os2:
      # type: unfeaturized

   Open questions:

   • What should be the default value for unfeaturized? I'd vote for false because we will otherwise breaking existing bots.

2. Deprecate UnfeaturizedSlot
   Open questions:

   • Should we introduce a slot type Any instead which can hold arbitrary values? I'd vote for yes. We can introduce a slot type Any which explicitly throws an error when used with unfeaturized: false. If users want to use an Any slot with unfeaturized: false, they need to implement their own slot type

3. Check whether / how this affects Rasa X / Rasa SDK

[wochinge]

@akelad @tmbo Please double check

We currently don't touch the slot values for Unfeaturized. Means if you feed a dictionary (e.g. as part of a custom action), then it will stay a dictionary

[wochinge]

Ok, let's featurize all slots by default (except the old UnfeaturizedSlot as we will break all existing bots otherwise.

[tmbo]

Ok, let's featurize all slots by default (except the old UnfeaturizedSlot as we will break all existing bots otherwise.

Yes this sounds reasonable.

Should we introduce a slot type Any instead which can hold arbitrary values? I'd vote for yes.

I'd agree. The unfeaturized slot type should stay and throw a deprecation warning.

Regarding the naming of the flag:

• I think it is easier to understand if a flags name is not negated, so featurized instead of unfeaturized
• Maybe we can come up with a better naming, e.g. influences_conversation or influences_prediction or something that is slightly less ml heavy speech?

[wochinge]

Both valid points 👍 I'd personally prefer imperative style and affect (e.g. affect_conversation) but maybe @erohmensing or @melindaloubser1 can help us out as native speakers.

[indam23]

I like "influence_conversation"; English speakers can never get their affects and effects sorted out anyway.

[wochinge]

Sounds good. Gonna go with that one then 👍

[wochinge]

@melindaloubser1 Just stumbled across this line:

rasa/rasa/shared/core/slots.py

Line 61 in 4782953

raise NotImplementedError(

It doesn't make sense to raise a NotImplementedError here. None except the CategoricalSlot currently implement this. Means this would explode for all other of the standard slots. I think it should rather be pass. any objections?

[wochinge]

pass also doesn't make sense. I'd just remove this from the parent class Slot, ok?