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In Voiceflow, a dialog state is assigned to a unique userID. This userID can be any string and is typically something unique that easily references the person on the session - such as an username, email, device ID, or phone number. (e.g. user54646, user@gmail.com, 1-647-424-4242, etc.). If you’re not sure what to call it just for testing purposes, you can just pick a random userID. The response schema consists of two main properties:
  1. Stack
  2. Variables
We will cover each property below, as well as an overview of the Voiceflow context model.

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Stack

The stack is an array of flows that are currently active in the conversation. Each flow contains:
  • programID: the ID of the flow, which can be found in the URL of the address bar https://creator.voiceflow.com/project/{versionID}/canvas/{programID}
  • nodeID: current block this flow is on
  • variables: flow-scoped variables
  • storage: internal flow parameters for runtime
  • commands
In the example below, you can see that there are three flows available on the stack (620e669eac2f70001cf9d85a, 620e669eac2f70001cf9d85b and 620e669eac2f70001cf9d85c) and we are currently sitting on flow 620e669eac2f70001cf9d85c, as denoted by the nodeID pointing to a block within this flow. Note: the programID of the first flow in the stack is always the versionID of the Agent. Example stack: 
{
  "stack": [
    {
      "nodeID": null,
      "programID": "620e669eac2f70001cf9d85a", //<-- versionID of the agent
      "storage": {},
      "commands": [],
      "variables": {}
    },
    {
      "nodeID": null,
      "programID": "620e669eac2f70001cf9d85b", //<-- starting flow
      "storage": {
          "output": [
              {
                  "children": [
                      {
                          "text": "What size?"
                      }
                  ]
              }
          ]
      },
      "commands": [],
      "variables": {}
    },
    {
      "nodeID": "61f40992f0e4e70a1f2328d1",
      "programID": "620e669eac2f70001cf9d85c",//<-- top-level flow
      "storage": {
          "outputMap": null,
          "output": [
              {
                  "children": [
                      {
                          "text": "You can get an additional pizza for half the price today. Would you like to do that?"
                      }
                  ]
              }
          ]
      },
      "commands": [],
      "variables": {
            "discount_code": "DEAL4TWO"
      }
    }
  ]
}

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Variables

The two ways you can create variable keys in your Interaction Model is through:
  1. Entities
  2. Variables
The difference between Entities and Variables is how they are assigned values at runtime. An entity value is assigned through a user interaction (e.g. utterance) whereas a variable is dynamically assigned a value from the design itself based on a user action (e.g. through an API call or custom code). Variable examples 
{
  "variables": {
    "type": "pepperoni",
    "size": "large",
    "amount": 6,
    "sessions": 0,
    "user_id": "1234",
    "timestamp": 1645112935,
    "platform": 0,
    "locale": 0,
    "side": 0,
    "intent_confidence": 100,
    "last_utterance": "large"
  }
}

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Voiceflow Context Model

In this video, we’ll explain Voiceflow’s entire Context Model in more detail.