Slots in Rasa Open Source 2.x

Video#

In Rasa, slots are your long term memory in a conversation. If there's any information you'd like to store for later use, you'd typically want to store it in a slot. It's important to understand that a slot is not the same thing as an entity. You could store any information in a slot, even if no entity has been detected. That said, it is very common to fill a slot value with an entity value.

If you want to define a slot, you'll need to define it in your domain.yml file.

slots:
  destination:
    type: text
    influence_conversation: false

You'll notice that in this configuration we've added a influence_conversation tag. The reason is that slots can influence a story. You might have something like this in your stories.yml file.

stories:
- story: booking a flight ticket
   steps:
   - intent: book_a_ticket
   - slot_was_set:
     - destination: Toronto

If your slots are configured to influence the flow of the conversation, you have to include them in your training stories.

Setting Slots#

Typically, your slot values will be set by detected entities. In these situations your domain.yml file should also include entities.

entities:
  - destination

slots:
  destination:
    type: text
    influence_conversation: false

This way, when an entity is detected it can fill in the slot value. You can also set slot values with custom actions, but we'll discuss how to do that in a later video.

Auto Fill#

By default, slots that have matching entity names will automatically be filled with the values of those entities. You can disable this behaviour by changing the configuration of the auto_fill parameter to false.

entities:
- destination


slots:
  destination
    type: text
    auto_fill: false

Types#

In Rasa, slots have types. This is useful, because certain types of information are better served as a number than a string of text.

Text Slots#

Slot type text can be used to store any text information. It can influence the conversation based on whether or not the slot has been set.

slots:
  destination:
    type: text
    influence_conversation: true

Boolean Slots#

Slot type boolean can be used to store information that can get the values True or False.

slots:
  authenticated:
    type: boolean
    influence_conversation: true

Categorical Slots#

Slot type categorical can be used to store values that can get one of a predefined set of possible values.

slots:
  price_range:
    type: categorical
    values:
      - low
      - medium
      - high

Float Slots#

Slot type float can be used to store numerical values.

slots:
  radius:
    type: float
    min_value: 0
    max_value: 100

List Slots#

List slots can be used to store a list of values. When configured, only the presence of the slot can have influence on the flow of the conversation. The values themselves won't be taken into account.

slots:
  items:
    type: list

'Any' Slots#

The "any" slot type can be used to store any arbitrary values. Slots of this type don’t have any influence on the conversation flow which means that the value and the presence of the slot doesn’t have any influence on how the conversation goes.

slots:
  shopping_items:
      type: any

Initial Values#

Finally, it's good to know that you can also set a default value on a slot by configuring the initial_value parameter. The value will be assigned to the slot from the beginning of the conversation and can be reset later on by NLU or custom actions.

slots:
  current_account:
      type: float
      initial_value: 100

Links#

• Rasa Slots Documentation

Exercises#

Try to answer the following questions to test your knowledge.

• When does a slot influence a conversation? When does it not?
• What's the difference between a slot and an entity?