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Solid Vocabulary Term Strategies: Trade-offs Matrix

This page outlines the trade-offs of different strategies for defining RDF predicates in Solid applications. It is intended to guide developers, app authors, and spec contributors in choosing appropriate approaches for various stages of development, from prototyping to standardization.

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🧭 1. Term Definition Strategies

Strategy	Example	Description
URN:solid	urn:solid:foo	A URN-based local identifier for rapid prototyping.
Pod-local URI	/profile/card#foo	A user- or app-local identifier, unique to the Pod domain.
Custom HTTP URI	https://app.example/vocab#foo	A hosted vocabulary term by the app or organization.
W3ID	https://w3id.org/solid/foo	Long-term stable URI under community control.
Global Standard	https://schema.org/name	Widely adopted and resolvable term managed externally.

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📊 2. Trade-offs Matrix

Criteria	URN:solid	Pod-local URI	Custom HTTP URI	W3ID	Global Standard
Simple for developers	✅	✅	✅	⚠️*	⚠️
Requires minting process	❌	❌	⚠️	✅	✅
Globally unique	❌	⚠️	✅	✅	✅
Dereferenceable	❌	✅	✅	✅	✅
Discoverable via RDF tooling	❌	⚠️	✅	✅	✅
Risk of collisions	⚠️	⚠️	✅	✅	✅
Privacy-preserving	✅	✅	⚠️	❌	❌
Best for interop across apps	❌	⚠️	✅	✅	✅
Works offline / air-gapped setups	✅	✅	⚠️	❌	❌
Encourages rapid prototyping	✅	✅	⚠️	❌*	❌
Stable long-term	❌	❌	⚠️	✅	✅

✅ = Yes / good
⚠️ = Possible, but trade-offs
❌ = No / not recommended for that use case

• feedback from Noel de Martin

I can prototype an app using a w3id vocabulary without registering it for real until the app is "done". I also disagree with all the ❌ on that column

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📦 3. Recommendation by Use Case

Use Case	Recommended Strategy
Internal app development	urn:solid:*, Pod-local
Early prototyping with real data	Pod-local or custom HTTP URI
Cross-app interoperability	Custom HTTP URI or W3ID
Public-facing specs or standards	W3ID or Global Standard
Privacy-focused / edge environments	Pod-local or URNs

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🛠 4. Migration Strategy

Encourage evolution of vocabularies over time:

• Move from urn:solid:* to custom HTTP URIs or W3ID as terms stabilize.
• Use owl:sameAs, rdfs:seeAlso, or JSON-LD @context to map terms.
• Provide tooling to validate and promote terms from local to global.

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This document is open for feedback. Please suggest improvements or propose edits via pull request or GitHub discussion.