WebDAV backend for persistence

[melvincarvalho]

Summary

WebDAV is a natural fit for solidos-lite persistence. It treats HTML files as first-class resources - no translation needed between data islands and Turtle.

Why WebDAV?

• GET - serve HTML with data island ✓
• PUT - save entire HTML file back ✓
• DELETE, MKCOL, COPY, MOVE - all just work ✓
• Widely deployed (Apache, Nginx, Nextcloud, NAS devices)
• Battle-tested protocol (RFC 4918)
• Native OS support (mount as drive on macOS/Windows)
• Much simpler than Solid's LDP semantics

Technical Findings

Browser Support

• Browsers can make PUT requests via Fetch/XHR
• Works for overwriting existing files
• Creating new files triggers CORS preflight

CORS Challenge

• Most WebDAV servers don't return CORS headers by default
• Workarounds:
  • Configure server-side CORS headers (Apache/Nginx)
  • Same-origin deployment
  • Use a proxy

Authentication

Method	Notes
Basic Auth	Simple, needs HTTPS
Digest Auth	Challenge-response
Bearer Token	Modern, needs server support

JavaScript Libraries

• webdav npm package (recommended, actively maintained)
• Raw Fetch/XHR for simple cases

Implementation Approach

Phase 1: Basic PUT support

// Intercept writes, serialize HTML with updated data island
async function saveToWebDAV(url, htmlContent) {
  const response = await fetch(url, {
    method: 'PUT',
    headers: { 'Content-Type': 'text/html; charset=utf-8' },
    body: htmlContent
  });
  return response.ok;
}

Phase 2: Serialize data island

1. Intercept fetcher.webOperation() for PUT/PATCH
2. Serialize RDF store back to Turtle
3. Update <script type="text/turtle"> in DOM
4. PUT entire HTML document

Phase 3: Authentication UI

• Prompt for WebDAV credentials
• Store in sessionStorage
• Add Authorization header to requests

Example Servers for Testing

• Apache mod_dav
• Nginx with dav_ext_module
• Nextcloud (needs CORS config)
• sabre/dav (PHP)
• Simple Python: wsgidav

Benefits Over Solid Servers

• No need for servers to understand data islands
• HTML file IS the resource (no translation)
• Simpler protocol, more deployment options
• Can use existing infrastructure

Related

• Support write operations (PUT/PATCH) for data islands #1 - Write operations support