# System Breakdown

**Project:** HAD Digital  
**Version:** 1.0.0  
**Date:** 2026-09-05  
**Owner:** Dr Kais Aldabbagh

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## System Overview

HAD Digital is a coordinated digital platform for Hospitalisation a Domicile (HAD) in oncology. It provides structured toxicity monitoring, clinical alerting, and care coordination for home-care cancer patients.

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## Subsystems

### 1. Frontend Subsystem

| Component | Description | Files |
|-----------|-------------|-------|
| HTML Interface | Main web page | static/index.html |
| CSS Styles | Responsive design | static/app.css |
| JavaScript Logic | Application logic | static/app.js |

**Dependencies:** None (self-contained)

**Interfaces:**
- IF-01: Patient UI (HTTP/HTML)
- IF-02: Clinician UI (HTTP/HTML)

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### 2. Backend Subsystem

| Component | Description | Files |
|-----------|-------------|-------|
| HTTP Server | Main server | app.py |
| Configuration | Config management | config_manager.py |
| Database | Data persistence | database.py |
| Authentication | User auth | user_store.py |
| CTCAE Engine | Toxicity grading | ctcae_engine.py |
| Alert Engine | Alert routing | alert_engine.py |
| Audit Logger | Audit trail | audit_logger.py |
| Demo Data | Demo seeder | seed_demo.py |

**Dependencies:** Frontend Subsystem, Database Subsystem

**Interfaces:**
- IF-03: REST API (HTTP/JSON)
- IF-05: CTCAE Engine (Python)
- IF-06: Alert Engine (Python)
- IF-09: Audit Logger (Python)

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### 3. Database Subsystem

| Component | Description | Files |
|-----------|-------------|-------|
| SQLite Database | Data storage | data/had.db |
| CTCAE Rules | Grading rules | data/ctcae_rules.json |
| Guidance Content | Patient guidance | guidance/guidance.json |

**Dependencies:** None (self-contained)

**Interfaces:**
- IF-04: SQLite Database (SQL)

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### 4. AI Adapter Subsystem

| Component | Description | Files |
|-----------|-------------|-------|
| Base Adapter | Interface | adapters/base.py |
| Stub Adapter | Offline demo | adapters/stub.py |
| GLM Adapter | Online AI | adapters/glm.py |

**Dependencies:** Backend Subsystem

**Interfaces:**
- IF-07: AI Adapter (HTTP/JSON)

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## Data Flow

```text
Patient/Clinician
       │
       ▼
   Frontend (HTML/CSS/JS)
       │
       ▼
   HTTP Server (app.py)
       │
       ├──► CTCAE Engine (ctcae_engine.py)
       │         │
       │         ▼
       │    Alert Engine (alert_engine.py)
       │
       ├──► Database (database.py)
       │         │
       │         ▼
       │    SQLite (had.db)
       │
       ├──► Audit Logger (audit_logger.py)
       │
       └──► AI Adapter (adapters/)
```

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## Integration Points

| From | To | Interface | Protocol |
|------|----|-----------|----------|
| Frontend | HTTP Server | IF-03 | HTTP/JSON |
| HTTP Server | Database | IF-04 | SQL |
| HTTP Server | CTCAE Engine | IF-05 | Python |
| HTTP Server | Alert Engine | IF-06 | Python |
| HTTP Server | AI Adapter | IF-07 | HTTP/JSON |
| HTTP Server | Audit Logger | IF-09 | Python |

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## Dependencies

### External Dependencies

None (pure Python standard library)

### Internal Dependencies

| Component | Depends On |
|-----------|------------|
| app.py | config_manager, database, user_store, ctcae_engine, alert_engine, audit_logger, seed_demo, adapters |
| database.py | config_manager |
| user_store.py | database |
| ctcae_engine.py | database |
| alert_engine.py | database |
| audit_logger.py | database |
| seed_demo.py | database |

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