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# Feature Engineering Specification

## Persistence &amp; Data Management Features

**Feature Group ID:** FG-DATA  
**Scope:** Sensor Hub (Sub-Hub only)  
**Target Platform:** ESP32-S3–based Sensor Hub  
**Applies To:** Indoor poultry farm sensor hubs  
**Dependencies:**

*   Sensor Data Acquisition (FG-DAQ)
    
*   Data Quality &amp; Calibration (FG-DQC)
    
*   Diagnostics &amp; Health Monitoring (FG-DIAG)
    
*   System State Management / Teardown Mechanism
    

## 1\. Purpose and Objectives

The **Persistence &amp; Data Management Features** define how the Sensor Hub stores, protects, and manages critical runtime and historical data. These features ensure that:

*   Sensor data and system state are not lost during resets or failures
    
*   Data storage is abstracted from application logic
    
*   Critical data is safely handled during firmware updates, configuration changes, or fatal faults
    

The persistence layer is a **foundational system service**, supporting diagnostics, calibration, OTA, and recovery operations.

## 2\. Feature Overview and Relationships

<figure class="table op-uc-figure_align-center op-uc-figure"><table class="op-uc-table"><thead class="op-uc-table--head"><tr class="op-uc-table--row"><th class="op-uc-table--cell op-uc-table--cell_head"><p class="op-uc-p">Feature ID</p></th><th class="op-uc-table--cell op-uc-table--cell_head"><p class="op-uc-p">Feature Name</p></th><th class="op-uc-table--cell op-uc-table--cell_head"><p class="op-uc-p">Primary Objective</p></th><th class="op-uc-table--cell op-uc-table--cell_head"><p class="op-uc-p">Related Features</p></th></tr></thead><tbody><tr class="op-uc-table--row"><td class="op-uc-table--cell"><p class="op-uc-p">F-DATA-01</p></td><td class="op-uc-table--cell"><p class="op-uc-p">Persistent Sensor Data Storage</p></td><td class="op-uc-table--cell"><p class="op-uc-p">Store timestamped sensor data</p></td><td class="op-uc-table--cell"><p class="op-uc-p">DAQ, COM</p></td></tr><tr class="op-uc-table--row"><td class="op-uc-table--cell"><p class="op-uc-p">F-DATA-02</p></td><td class="op-uc-table--cell"><p class="op-uc-p">Data Persistence Abstraction (DP)</p></td><td class="op-uc-table--cell"><p class="op-uc-p">Abstract storage access</p></td><td class="op-uc-table--cell"><p class="op-uc-p">Application Layer</p></td></tr><tr class="op-uc-table--row"><td class="op-uc-table--cell"><p class="op-uc-p">F-DATA-03</p></td><td class="op-uc-table--cell"><p class="op-uc-p">Safe Data Handling During State Transitions</p></td><td class="op-uc-table--cell"><p class="op-uc-p">Protect data during teardown</p></td><td class="op-uc-table--cell"><p class="op-uc-p">OTA, System Mgmt</p></td></tr></tbody></table></figure>

## 3\. Functional Feature Descriptions

### 3.1 F-DATA-01: Persistent Sensor Data Storage

**Description**  
The system shall persist timestamped sensor data to non-volatile storage to support historical analysis, diagnostics correlation, and recovery scenarios.

Persistence may include:

*   Filtered sensor values
    
*   Timestamps
    
*   Sensor validity and status metadata
    

The persistence policy (frequency, retention window, overwrite behavior) is configurable and optimized for storage longevity and performance.

**Key Capabilities**

*   Non-volatile storage (SD card / NVM)
    
*   Timestamped records
    
*   Configurable retention policy
    
*   Integration with DAQ and COM
    

### 3.2 F-DATA-02: Data Persistence Abstraction (DP Component)

**Description**  
The system shall provide a **Data Persistence (DP) component** that abstracts storage access for all upper layers. Application and feature modules interact with the DP component rather than directly accessing storage hardware.

The DP component manages:

*   Data model definitions
    
*   Serialization and deserialization
    
*   Storage backend selection
    
*   Consistency and integrity guarantees
    

**Key Capabilities**

*   Unified persistence API
    
*   Storage backend abstraction
    
*   Centralized data ownership
    
*   Reduced coupling between layers
    

### 3.3 F-DATA-03: Safe Data Handling During State Transitions

**Description**  
The system shall ensure safe and deterministic handling of data during critical state transitions, including:

*   Firmware updates (OTA)
    
*   Machine Constants updates
    
*   System resets
    
*   Fatal error handling
    

Before entering such transitions, the system executes a controlled data finalization process to flush buffers, persist critical state, and verify data integrity.

**Key Capabilities**

*   Controlled data flush
    
*   Atomic write operations
    
*   Data integrity checks
    
*   Coordination with teardown mechanism
    

## 4\. System Requirements (Formal SHALL Statements)

### 4.1 Persistent Sensor Data Storage

**SR-DATA-001**  
The system shall persist timestamped sensor data in non-volatile storage.

**SR-DATA-002**  
The system shall store sensor data together with sensor identifiers, timestamps, and validity status.

**SR-DATA-003**  
The system shall support configurable data retention and overwrite policies.

### 4.2 Data Persistence Abstraction (DP Component)

**SR-DATA-004**  
The system shall provide a Data Persistence (DP) component as the sole interface for persistent data access.

**SR-DATA-005**  
The system shall prevent application and feature modules from directly accessing storage hardware.

**SR-DATA-006**  
The DP component shall support serialization and deserialization of structured system data.

### 4.3 Safe Data Handling During State Transitions

**SR-DATA-007**  
The system shall ensure that all critical runtime data is flushed to non-volatile storage before entering a controlled teardown or reset.

**SR-DATA-008**  
The system shall protect data integrity during firmware updates and configuration changes.

**SR-DATA-009**  
The system shall verify successful data persistence before completing a state transition.

## 5\. Feature ↔ System Requirement Mapping

<figure class="table op-uc-figure_align-center op-uc-figure"><table class="op-uc-table"><thead class="op-uc-table--head"><tr class="op-uc-table--row"><th class="op-uc-table--cell op-uc-table--cell_head"><p class="op-uc-p">Feature ID</p></th><th class="op-uc-table--cell op-uc-table--cell_head"><p class="op-uc-p">System Requirements</p></th></tr></thead><tbody><tr class="op-uc-table--row"><td class="op-uc-table--cell"><p class="op-uc-p">F-DATA-01</p></td><td class="op-uc-table--cell"><p class="op-uc-p">SR-DATA-001, SR-DATA-002, SR-DATA-003</p></td></tr><tr class="op-uc-table--row"><td class="op-uc-table--cell"><p class="op-uc-p">F-DATA-02</p></td><td class="op-uc-table--cell"><p class="op-uc-p">SR-DATA-004, SR-DATA-005, SR-DATA-006</p></td></tr><tr class="op-uc-table--row"><td class="op-uc-table--cell"><p class="op-uc-p">F-DATA-03</p></td><td class="op-uc-table--cell"><p class="op-uc-p">SR-DATA-007, SR-DATA-008, SR-DATA-009</p></td></tr></tbody></table></figure>

## 6\. Engineering Notes

*   The DP component aligns with your **DP Stack** already defined in the architecture.
    
*   Atomic write strategies (e.g., temp file + rename) are recommended.
    
*   Diagnostic events should be generated on persistence failures.
    
*   Storage wear-leveling considerations apply for SD/NVM.
    

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