Slots
Slots
Slots are your bot’s memory. They act as a key-value store which can be used to store information the user provided (e.g their home city) as well as information gathered about the outside world (e.g. the result of a database query).
Most of the time, you want slots to influence how the dialogue progresses. There are different slot types for different behaviors.
For example, if your user has provided their home city, you might have a text slot called home_city. If the user asks for the weather, and you don’t know their home city, you will have to ask them for it. A text slot only tells Rasa Core whether the slot has a value. The specific value of a text slot (e.g. Bangalore or New York or Hong Kong) doesn’t make any difference.
If the value itself is important, use a categorical or a bool slot. There are also float, and list slots. If you just want to store some data, but don’t want it to affect the flow of the conversation, use an unfeaturized slot.
How Rasa Uses Slots
The Policy doesn’t have access to the value of your slots. It receives a featurized representation. As mentioned above, for a text slot the value is irrelevant. The policy just sees a 1 or 0 depending on whether it is set.
You should choose your slot types carefully!
How Slots Get Set
You can provide an initial value for a slot in your domain file:
slots:
name:
type: text
initial_value: "human"
There are multiple ways that slots are set during a conversation:
Slots Set from NLU
If your NLU model picks up an entity, and your domain contains a slot with the same name, the slot will be set automatically. For example:
# story_01
* greet{"name": "Ali"}
- slot{"name": "Ali"}
- utter_greet
Slots Set By Clicking Buttons
You can use buttons as a shortcut. Rasa Core will send messages starting with a / to the RegexInterpreter, which expects NLU input in the same format as in story files, e.g. /intent{entities}. For example, if you let users choose a color by clicking a button, the button payloads might be /choose{"color": "blue"} and /choose{"color": "red"}.
You can specify this in your domain file like this:
utter_ask_color:
- text: "what color would you like?"
buttons:
- title: "blue"
payload: '/choose{"color": "blue"}'
- title: "red"
payload: '/choose{"color": "red"}'
Slots Set by Actions
The second option is to set slots by returning events in custom actions. In this case, your stories need to include the slots. For example, you have a custom action to fetch a user’s profile, and you have a categorical slot called account_type.
When the fetch_profile action is run, it returns a rasa.core.events.SlotSet event:
slots:
account_type:
type: categorical
values:
- premium
- basic
from rasa_sdk.actions import Action
from rasa_sdk.events import SlotSet
import requests
class FetchProfileAction(Action):
def name(self):
return "fetch_profile"
def run(self, dispatcher, tracker, domain):
url = "http://myprofileurl.com"
data = requests.get(url).json
return [SlotSet("account_type", data["account_type"])]
# story_01
* greet
- action_fetch_profile
- slot{"account_type" : "premium"}
- utter_welcome_premium
# story_02
* greet
- action_fetch_profile
- slot{"account_type" : "basic"}
- utter_welcome_basic
In this case you do have to include the - slot{} part in your stories. Rasa Core will learn to use this information to decide on the correct action to take (in this case, utter_welcome_premium or utter_welcome_basic).
Note: It is very easy to forget about slots if you are writing stories by hand. We strongly recommend that you build up these stories using Interactive Learning with Forms rather than writing them.
Slot Types
Text Slot
text Use For: User preferences where you only care whether or not they’ve been specified.
Example:
slots:
cuisine:
type: text
Description: Results in the feature of the slot being set to 1 if any value is set. Otherwise the feature will be set to 0 (no value is set).
Boolean Slot
bool Use For: True or False
Example:
slots:
is_authenticated:
type: bool
Description: Checks if slot is set and if True
Categorical Slot
categorical Use For: Slots which can take one of N values
Example:
slots:
risk_level:
type: categorical
values:
- low
- medium
- high
Description: Creates a one-hot encoding describing which of the values matched.
Float Slot
float Use For: Continuous values
Example:
slots:
temperature:
type: float
min_value: -100.0
max_value: 100.0
Defaults: max_value=1.0, min_value=0.0
Description: All values below min_value will be treated as min_value, the same happens for values above max_value.
List Slot
list Use For: Lists of values
Example:
slots:
shopping_items:
type: list
Description: The feature of this slot is set to 1 if a value with a list is set, where the list is not empty.
Unfeaturized Slot
unfeaturized Use For: Data you want to store which shouldn’t influence the dialogue flow
Example:
slots:
internal_user_id:
type: unfeaturized
Description: There will not be any featurization of this slot, hence its value does not influence the dialogue flow.
Custom Slot Types
Maybe your restaurant booking system can only handle bookings for up to 6 people. In this case you want the value of the slot to influence the next selected action (and not just whether it’s been specified). You can do this by defining a custom slot class.
In the code below, we define a slot class called NumberOfPeopleSlot:
from rasa.core.slots import Slot
class NumberOfPeopleSlot(Slot):
def feature_dimensionality(self):
return 2
def as_feature(self):
r = [0.0] * self.feature_dimensionality()
if self.value:
if self.value <= 6:
r[0] = 1.0
else:
r[1] = 1.0
return r
Now we also need some training stories:
# story1
...
* inform{"people": "3"}
- action_book_table
...
# story2
* inform{"people": "9"}
- action_explain_table_limit
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