# Multi-Database Architecture for bronhouder.nl

This document describes the multi-database architecture implemented for the GLAM data platform at bronhouder.nl.

## Overview

The Database page (`/database`) provides a unified interface for exploring heritage custodian data across four different database systems, each optimized for different use cases:

```
┌─────────────────────────────────────────────────────────────────┐
│                     bronhouder.nl/database                       │
├─────────────────────────────────────────────────────────────────┤
│  ┌──────────┐  ┌──────────┐  ┌──────────┐  ┌──────────┐        │
│  │ 🦆 DuckDB│  │🐘Postgres│  │ 🧠 TypeDB│  │🔗Oxigraph│        │
│  │ (Browser)│  │ (Server) │  │ (Server) │  │ (Server) │        │
│  └────┬─────┘  └────┬─────┘  └────┬─────┘  └────┬─────┘        │
│       │             │             │             │               │
│  In-Browser     REST API      REST API      SPARQL             │
│  WASM           Proxy         Proxy         Endpoint           │
└───────┼─────────────┼─────────────┼─────────────┼───────────────┘
        │             │             │             │
        ▼             ▼             ▼             ▼
   ┌─────────┐  ┌──────────┐  ┌──────────┐  ┌──────────┐
   │ Browser │  │PostgreSQL│  │  TypeDB  │  │ Oxigraph │
   │ Memory  │  │ Database │  │ Database │  │  Store   │
   └─────────┘  └──────────┘  └──────────┘  └──────────┘
```

## Database Systems

### 1. DuckDB (In-Browser OLAP)

**Status**: ✅ Fully Operational

**Technology**: DuckDB-WASM running entirely in the browser

**Use Cases**:
- Ad-hoc SQL analytics on heritage institution data
- Fast aggregations and filtering
- Data exploration without server round-trips

**Data Source**: `/data/nde_institutions.json` (10.8 MB, 1,863 institutions)

**Features**:
- Upload JSON/CSV/Parquet files directly
- Run SQL queries in-browser
- No server dependency
- Export query results

**Hook**: `frontend/src/hooks/useDuckDB.ts`

**Panel**: `frontend/src/components/database/DuckDBPanel.tsx`

### 2. PostgreSQL (Relational)

**Status**: ✅ Fully Operational (as of 2025-12-06)

**Technology**: PostgreSQL 16.11 with FastAPI REST proxy

**Endpoint**: `https://bronhouder.nl/api/postgres`

**Use Cases**:
- Complex relational queries
- Full-text search on institution names
- Transactional operations
- Integration with existing tools

**Data**: 1,838 NDE heritage institutions with:
- 32 columns including coordinates, ratings, reviews
- GHCID identifiers (text, UUID, numeric)
- JSONB fields for wikidata_types, reviews, identifiers, genealogiewerkbalk

**API Endpoints**:
- `GET /` - Health check and statistics
- `POST /query` - Execute SQL query (read-only SELECT/WITH)
- `GET /tables` - List all tables with metadata
- `GET /schema/{table}` - Get table schema
- `GET /stats` - Detailed database statistics

**Backend**: `/opt/glam-backend/postgres/` on server
- `main.py` - FastAPI application
- `load_nde_data.py` - Data loading script
- Systemd service: `glam-postgres-api.service`

**Hook**: `frontend/src/hooks/usePostgreSQL.ts`

**Panel**: `frontend/src/components/database/PostgreSQLPanel.tsx`

### 3. Oxigraph (RDF/SPARQL)

**Status**: ✅ Fully Operational

**Technology**: Oxigraph SPARQL endpoint on server

**Use Cases**:
- Linked Data queries
- Ontology exploration
- Cross-referencing with Wikidata, Schema.org
- Semantic reasoning

**Endpoint**: `https://bronhouder.nl/sparql` (proxied to 91.98.224.44:7878)

**Triple Count**: 426,243 triples

**Features**:
- SPARQL 1.1 query interface
- Graph exploration
- Namespace prefix management
- RDF upload (Turtle, N-Triples, JSON-LD)

**Hook**: `frontend/src/hooks/useOxigraph.ts`

**Panel**: `frontend/src/components/database/OxigraphPanel.tsx`

### 3. PostgreSQL (Relational)

**Status**: ⏳ Requires Backend API

**Technology**: PostgreSQL database with REST API proxy

**Use Cases**:
- Complex relational queries
- Full-text search
- Transactional operations
- Integration with existing tools

**Required**: REST API at `/api/postgres` or `VITE_POSTGRES_API_URL`

**Planned Features**:
- Table/schema browser
- SQL query interface
- Query history
- Export to CSV

**Hook**: `frontend/src/hooks/usePostgreSQL.ts`

**Panel**: `frontend/src/components/database/PostgreSQLPanel.tsx`

### 4. TypeDB (Knowledge Graph)

**Status**: ⏳ Deferred - Server has only 3.7GB RAM, TypeDB requires 4GB+

**Technology**: TypeDB with REST API proxy

**Use Cases**:
- Complex knowledge graph queries
- Multi-hop relationship traversal
- Temporal reasoning (organizational changes)
- Entity resolution

**Note**: To enable TypeDB, upgrade server to cx32 (8GB RAM) or higher.

**Hook**: `frontend/src/hooks/useTypeDB.ts`

**Panel**: `frontend/src/components/database/TypeDBPanel.tsx`

## Frontend Components

### Database Page (`/database`)

The main Database page provides:

1. **Tab Navigation**: Switch between database views
2. **All Databases Overview**: Comparison grid with status indicators
3. **Individual Database Panels**: Full-featured interface for each system

### Component Structure

```
frontend/src/
├── pages/
│   ├── Database.tsx        # Main page with tab navigation
│   └── Database.css        # Styles for all database components
├── hooks/
│   ├── useDuckDB.ts        # DuckDB-WASM hook
│   ├── useOxigraph.ts      # Oxigraph SPARQL hook
│   ├── usePostgreSQL.ts    # PostgreSQL REST hook
│   └── useTypeDB.ts        # TypeDB REST hook
└── components/database/
    ├── DuckDBPanel.tsx     # DuckDB interface
    ├── OxigraphPanel.tsx   # Oxigraph interface
    ├── PostgreSQLPanel.tsx # PostgreSQL interface
    ├── TypeDBPanel.tsx     # TypeDB interface
    └── index.ts            # Exports
```

## Data Flow

### NDE Institution Data

```
YAML Files (data/nde/enriched/entries/)
    │
    ├── scripts/export_nde_for_duckdb.py
    │   └── frontend/public/data/nde_institutions.json (DuckDB)
    │
    ├── scripts/nde_to_hc_rdf.py
    │   └── data/nde/rdf/*.ttl → Oxigraph
    │
    └── [Future] scripts/nde_to_typedb.py
        └── TypeDB
```

### LinkML Schema

```
schemas/20251121/linkml/
├── 01_custodian_name_modular.yaml    # Main ontology schema
├── nde_enriched_entry.yaml           # NDE entry schema
└── modules/                          # Modular components
```

## API Contracts

### PostgreSQL REST API (Required)

```typescript
// Expected endpoints
POST /api/postgres/query
{
  "sql": "SELECT * FROM institutions LIMIT 10"
}
// Response: { rows: [...], columns: [...] }

GET /api/postgres/tables
// Response: { tables: [...] }

GET /api/postgres/schema/:table
// Response: { columns: [...] }
```

### TypeDB REST API (Required)

```typescript
// Expected endpoints
POST /api/typedb/query
{
  "query": "match $x isa institution; get $x; limit 10;"
}
// Response: { results: [...] }

GET /api/typedb/schema
// Response: { entity_types: [...], relation_types: [...] }

GET /api/typedb/entity-types
// Response: { types: [...] }
```

## Environment Variables

```bash
# Frontend (.env)
VITE_SPARQL_ENDPOINT=https://bronhouder.nl/sparql
VITE_POSTGRES_API_URL=https://bronhouder.nl/api/postgres
VITE_TYPEDB_API_URL=https://bronhouder.nl/api/typedb
```

## Server Infrastructure

```
Server: 91.98.224.44 (Hetzner cx22)
├── Caddy (reverse proxy)
│   ├── / → /var/www/glam-frontend/
│   ├── /sparql → localhost:7878 (Oxigraph)
│   └── /api → localhost:8000 (FastAPI)
├── Oxigraph (port 7878)
├── GLAM API (port 8000)
└── [Future] PostgreSQL, TypeDB
```

## Deployment

```bash
# Deploy frontend only
./infrastructure/deploy.sh --frontend

# Check status
./infrastructure/deploy.sh --status

# Deploy everything
./infrastructure/deploy.sh --all
```

## Next Steps

1. **PostgreSQL Backend**: Create FastAPI endpoints for PostgreSQL queries
2. **TypeDB Backend**: Create FastAPI endpoints for TypeDB queries
3. **Data Sync**: Implement data loading scripts for PostgreSQL/TypeDB
4. **Query Builder**: Add visual query builder for non-technical users
5. **Export**: Enable data export in multiple formats

## Related Documentation

- [AGENTS.md](../AGENTS.md) - AI agent instructions
- [DEPLOYMENT_GUIDE.md](./DEPLOYMENT_GUIDE.md) - Deployment procedures
- [SCHEMA_MODULES.md](./SCHEMA_MODULES.md) - LinkML schema architecture