A teacher in Kabul and an employer in Berlin can both check what you can do, and why.

• Read the specification
• Run the test vectors
• Try the explainer
• Participate

The problem§

Many people can do things they cannot prove. Papers are lost, institutions close, states stop recognising study, and a certificate says little about how it was earned. Employers and universities cannot easily check what stands behind a claim, so they trust brands and borders instead of evidence.

A worked example

An invented learner claims level 4 in a first course in real analysis. The verifier applies the default policy: at least two admissible attestors, one live sitting, attestors with at least three sittings.

Evidence and attestations

Item	Kind	Attestations
E1	Practice runs (replayable) 40 seeded epsilon-delta exercises, replayed from their seeds	replayed from seeds, no attestor needed
E2	Live sitting Live sitting S-2026-014: 90 minutes, two examiners, whiteboard stroke log	Ember (examiner): level 4 Ash (examiner): level 4
E3	Reviewed work Proof portfolio: three written proofs (hash of the PDF)	Linden (reviewer): level 4
E4	Peer review Peer review by a fellow learner	Fern (fellow learner): level 3 ignored (only 1 sitting(s), policy needs 3)

recognised level 4 of 5 · confidence 0.909 · 3 independent attestors · live sitting present

Show the step-by-step explanation (rules R1 to R7)

1. R1 Checked 4 evidence item(s) and 4 attestation(s): every hash, every reveal against its commitment, and the chain. 0 failed.
2. R2 Attestor did:sanad:fern (attestation att-04) was ignored: only 1 sitting(s), policy needs 3.
3. R2 4 attestation(s) and automatic record(s) are admissible on 3 evidence item(s).
4. R3 Evidence E1 is 1.77 month(s) old: age factor 0.950 (half-life 24 months).
5. R4 Evidence E1 (auto): levels [3], lower median 3 -> level 3.
6. R3 Evidence E2 is 0.59 month(s) old: age factor 0.983 (half-life 24 months).
7. R4 Evidence E2 (sitting): levels [4,4], lower median 4 -> level 4.
8. R3 Evidence E3 is 1.18 month(s) old: age factor 0.966 (half-life 24 months).
9. R4 Evidence E3 (artifact): levels [4], lower median 4 -> level 4.
10. R4 Evidence E4 has no admissible attestation, so it does not count.
11. R5 3 distinct admissible attestor(s) (did:sanad:ash, did:sanad:ember, did:sanad:linden); policy needs 2 and a live sitting, which is present. Independence is met.
12. R6 Recognised level = the lower of the claim (4) and the lower median of the live-sitting and artifact evidence levels ([4,4]) = 4.
13. R7 Confidence = 1 - the product of (1 - weight x age factor x agreement factor) over 4 item(s) = 0.909.

All people and data are invented. The result is computed when this page is built, by the reference code in reference/; node reference/verify.mjs reproduces it. Appendix A of the specification describes the same example.

How it works§

1. ClaimA person states a skill at a level, for example real analysis at level 4. The skill is a node in an open, versioned concept graph.
2. EvidenceThe claim is backed by typed evidence: replayable practice runs, a live sitting watched by examiners, reviewed work, peer review.
3. AttestationAttestors sign what they saw. Marks are committed blind before any is revealed, so that they are independent of one another.
4. RecognitionAnyone runs the published function with their own policy and gets a level, a confidence and a step-by-step explanation.

Who it is for§

Where to start§

• Read the specification (about 20 minutes) or its PDF.
• Run node reference/verify.mjs from the conformance page to see 20 vectors pass.
• Open the explainer to change a verifier policy and watch the result and its explanation change.
• Read the questions and answers, the roadmap and how to participate.