Understanding Amazon Lex V2 bot sessions
When a user starts a conversation with your bot, Amazon Lex V2 creates a
session. The information exchanged between your
application and Amazon Lex V2 makes up the session state for the conversation.
When you make a request, the session is identified by an identifier that
you specify. For more information about the session identifier, see the
sessionId
field in the RecognizeText or
RecognizeUtterance operation.
You can modify the session state sent between your application and your bot. For example, you can create and modify session attributes that contain custom information about the session, and you can change the flow of the conversation by setting the dialog context to interpret the next utterance.
There are three ways that you can update session state.
-
Pass the session information inline as part of a call to the
RecognizeText
orRecognizeUtterance
operation. -
Use a Lambda function with the
RecognizeText
orRecognizeUtterance
operation that is called after each turn of the conversation. For more information, see Integrating an AWS Lambda function into your bot. The other is to use the Amazon Lex V2 runtime API in your application to make changes to the session state. -
Use operations that enable you to manage session information for a conversation with your bot. The operations are the PutSession operation, the GetSession operation, and the DeleteSession operation. You use these operations to get information about the state of your user's session with your bot, and to have fine-grained control over the state.
Use the GetSession
operation when you want to get the
current state of the session. The operation returns the current state of
the session, including the state of the dialog with your user, any
session attributes that have been set and slot values for the current
intent and any other intents that Amazon Lex V2 has identified as possible
intents that match the user's utterance.
The PutSession
operation enables you to directly
manipulate the current session state. You can set the session, including
the type of dialog action that the bot will perform next and the
messages that Amazon Lex V2 sends to the user. This gives you control over the
flow of the conversation with the bot. Set the dialog action
type
field to Delegate
to have Amazon Lex V2
determine the next action for the bot.
You can use the PutSession
operation to create a new
session with a bot and set the intent that the bot should start with.
You can also use the PutSession
operation to change from
one intent to another. When you create a session or change the intent
you also can set session state, such as slot values and session
attributes. When the new intent is finished, you have the option of
restarting the prior intent.
The response from the PutSession
operation contains the
same information as the RecognizeUtterance
operation. You
can use this information to prompt the user for the next piece of
information, just as you would with the response from the
RecognizeUtterance
operation.
Use the DeleteSession
operation to remove an existing
session and start over with a new session. For example, when you are
testing your bot you can use the DeleteSession
operation to
remove test sessions from your bot.
The session operations work with your fulfillment Lambda functions. For
example, if your Lambda function returns Failed
as the
fulfillment state you can use the PutSession
operation to
set the dialog action type to close
and
fulfillmentState
to ReadyForFulfillment
to
retry the fulfillment step.
Here are some things that you can do with the session operations:
-
Have the bot start a conversation instead of waiting for the user.
-
Switch intents during a conversation.
-
Return to a previous intent.
-
Start or restart a conversation in the middle of the interaction.
-
Validate slot values and have the bot re-prompt for values that are not valid.
Each of these are described further below.
Starting a new session
If you want to have the bot start the conversation with your user,
you can use the PutSession
operation.
-
Create a welcome intent with no slots and a conclusion message that prompts the user to state an intent. For example, "What would you like to order? You can say 'Order a drink' or 'Order a pizza.'"
-
Call the
PutSession
operation. Set the intent name to the name of your welcome intent and set the dialog action toDelegate
. -
Amazon Lex will respond with the prompt from your welcome intent to start the conversation with your user.
Switching intents
You can use the PutSession
operation to switch from
one intent to another. You can also use it to switch back to a
previous intent. You can use the PutSession
operation
to set session attributes or slot values for the new intent.
-
Call the
PutSession
operation. Set the intent name to the name of the new intent and set the dialog action toDelegate
. You can also set any slot values or session attributes required for the new intent. -
Amazon Lex will start a conversation with the user using the new intent.
Resuming a prior intent
To resume a prior intent you use the GetSession
operation to get the state of the intent, perform the needed
interaction, and then use the PutSession
operation to
set the intent to its previous dialog state.
-
Call the
GetSession
operation. Store the state of the intent. -
Perform another interaction, such as fulfilling a different intent.
-
Using the information saved information for the previous intent, call the
PutSession
operation. This will return the user to the previous intent in the same place in the conversation.
In some cases it may be necessary to resume your user's conversation with your bot. For example, say that you have created a customer service bot. Your application determines that the user needs to talk to a customer service representative. After talking to the user, the representative can direct the conversation back to the bot with the information that they collected.
To resume a session, use steps similar to these:
-
Your application determines that the user needs to speak to a customer service representative.
-
Use the
GetSession
operation to get the current dialog state of the intent. -
The customer service representative talks to the user and resolves the issue.
-
Use the
PutSession
operation to set the dialog state of the intent. This may include setting slot values, setting session attributes, or changing the intent. -
The bot resumes the conversation with the user.
Validating slot values
You can validate responses to your bot using your client
application. If the response isn't valid, you can use the
PutSession
operation to get a new response from
your user. For example, suppose that your flower ordering bot can
only sell tulips, roses, and lilies. If the user orders carnations,
your application can do the following:
-
Examine the slot value returned from the
PostText
orPostContent
response. -
If the slot value is not valid, call the
PutSession
operation. Your application should clear the slot value, set theslotToElicit
field, and set thedialogAction.type
value toelicitSlot
. Optionally, you can set themessage
andmessageFormat
fields if you want to change the message that Amazon Lex uses to elicit the slot value.