Accessible Surveys

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Resuming Incomplete Surveys ​

When participating in a survey, respondents may close their browser, lose internet connection, or switch networks (such as moving from Wi-Fi to mobile data) before finishing. Accessible Surveys is designed to ensure that respondents can return to an incomplete survey and pick up exactly where they left off without losing their entered answers.

This document explains the technical and conceptual architecture that guarantees progress persistence and survey resumption.

Core Guarantee: Seamless Resumption ​

When a participant leaves an incomplete survey—even if they close the browser tab or completely power off their device—re-opening the original survey link allows them to resume from their last visited page with all previously answered questions intact.

INFO

Session progress is saved automatically after every question interaction or page navigation. Respondents do not need to manually click a "Save" button.

How Resumption Works Behind the Scenes ​

The state persistence engine relies on three coordinated mechanisms:

text
+--------------------------------------------------------------------------+
|                            Respondent Client                             |
|  1. Firebase Auth UID stored in persistent Browser Storage (IndexedDB)  |
+--------------------------------------------------------------------------+
                                     |
                                     v
+--------------------------------------------------------------------------+
|                         Firestore / Realtime DB                          |
|  2. State Machine Actor (surveyMachine & formMachine) snapshot saved     |
|     Indexed by: UID + Survey ID / Batch ID                               |
+--------------------------------------------------------------------------+
                                     |
                                     v
+--------------------------------------------------------------------------+
|                           Survey Rehydration                             |
|  3. Re-opening link restores UID, fetches active Actor, rehydrates state |
+--------------------------------------------------------------------------+

1. Anonymous & Authenticated User Identifiers (UID) ​

When a participant opens a survey link:

  • Anonymous Accounts (Default): The application automatically creates a persistent anonymous authentication session via Firebase Auth. A unique User Identifier (UID) is generated and stored locally in the browser's persistent storage (IndexedDB).
  • Personal / Verified Accounts: If the survey requires sign-in, the respondent authenticates with their email or identity provider, assigning their personal UID to the session.

2. Real-Time State Machine Sync ​

Every survey session is backed by state machine actors (surveyMachine and formMachine). As the participant fills in fields, checks choices, or advances pages:

  • State transitions record current page indices, visited questions, hidden statuses, and input values.
  • The state machine snapshot is synchronized in real-time to Cloud Firestore and Firebase Realtime Database.

3. Session Query and Rehydration ​

When the participant re-opens the survey link:

  1. The client retrieves the existing UID from local browser storage.
  2. The application queries Firestore (fetchActor) for an existing state machine actor snapshot matching that UID and the survey's batchId / buildId.
  3. If an existing actor snapshot is found, the survey engine skips initialization and rehydrates the saved state—restoring answered fields and placing the user back on the page where they left off.

Technical Factor Breakdown: What Enables Resumption? ​

To clarify how different environmental factors affect resumption, consider the matrix below:

FactorUsed to Resume?Details
Browser StorageYesStores the Firebase Authentication token (UID) in local storage / IndexedDB.
Cloud DatabaseYesStores the state machine snapshot (responses, page index, visited questions) linked to the UID.
Physical DeviceIndirectlyLocal browser storage resides on the specific device and browser profile used.
Wi-Fi / IP AddressNoAccessible Surveys never uses IP addresses or Wi-Fi networks to identify sessions.

Scenario Analysis ​

1. Closing the Browser or Restarting the Device ​

  • Can the participant resume? Yes.
  • Mechanism: Firebase Authentication stores credentials persistently in browser local storage (IndexedDB). When the user opens the browser and clicks the survey link again, the token is read from storage, retrieving the actor snapshot from Firestore.

2. Switching Wi-Fi or Cellular Networks ​

  • Can the participant resume? Yes.
  • Mechanism: Network switches (e.g., leaving home Wi-Fi and switching to 5G cellular data or connecting to a coffee shop Wi-Fi) change the device's IP address. Because Accessible Surveys identifies respondents via authenticated session tokens (UID) rather than network addresses, network changes have zero impact on survey progress or resumption.

3. Switching Browsers or Devices ​

  • Anonymous Surveys:
    • Opening the link on a different browser (e.g., switching from Safari to Chrome) or on a different device creates a new anonymous session, as anonymous auth tokens cannot cross browser boundaries.
  • Authenticated Surveys:
    • If the survey requires a personal account or uses personalized email tokens, logging in or using the personal link on any device retrieves the same Firestore actor snapshot tied to that account UID, enabling cross-device resumption.

Privacy & Security Benefits ​

  • No Privacy-Invasive Tracking: By avoiding IP address matching or network fingerprinting, Accessible Surveys respects user privacy and complies with strict GDPR guidelines.
  • Data Security: Response snapshots in Firestore are protected by Firebase Security Rules, ensuring only the authenticated UID (or authorized survey administrators) can access or write to the active session.

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