---
title: "Glossary"
description: "Short definitions of the terms QWED uses: fail-closed, admission, VERIFIED, UNVERIFIABLE, BLOCKED, proof_ref, attestation, formal statement and more."
url: https://qwedai.com/glossary
---

# Glossary

The terms QWED uses, each defined once. Other pages, the documentation and the READMEs use them in these senses.

[Deterministic verification](#deterministic-verification)

Checking a claim with a solver, parser or fixed rule, so the same input always gives the same result. No model decides whether the claim holds. [Engines](https://qwedai.com/engines)

[Fail-closed](#fail-closed)

Every outcome other than a completed, positive result stops the action by default, including errors, timeouts, inputs the check cannot handle and cases no rule covers. [What fail-closed means for AI checks](https://qwedai.com/guides/fail-closed)

[Fail-open](#fail-open)

When a check cannot finish, the action goes ahead as if the check had passed. Reasonable for advice a person will review; risky for actions a system takes on its own. [When fail-open is fine](https://qwedai.com/guides/fail-closed#open)

[Verdict](#verdict)

What a check established about a claim: VERIFIED, UNVERIFIABLE or BLOCKED. It is kept separate from the admission decision.

[VERIFIED](#verified)

The claim was proven deterministically, either true or false. It always carries a proof\_ref. VERIFIED on its own does not mean allowed.

[UNVERIFIABLE](#unverifiable)

The claim could not be proven either way: outside the engines, ambiguous, supported only by a model, or the solver timed out. Never admitted.

[BLOCKED](#blocked)

The check could not be run at all: the input did not parse, a setting or dependency was missing, or a policy forbids it. Never admitted.

[Admission](#admission)

The decision whether the checked output may be acted on: ADMIT or DENY. Only a VERIFIED result whose claim holds is admitted.

[VERIFIED · DENY](#verified-deny)

Proven, and what was proven is that the claim is false or unsafe, for example a SQL statement proven to delete data. The proof is the reason it is denied.

[Enforcement](#enforcement)

Acting on the admission decision. QWED returns the decision; the integration, a CI gate or a QWED product such as QWED Security enforces it.

[Formal statement](#formal-statement)

The precise version of a claim that an engine can check, such as an equation or a logic formula. QWED verifies the formal statement, not what someone meant by it.

[Untrusted translator](#untrusted-translator)

A language model used only to turn natural language into a formal statement. Its output is treated as untrusted: the translation is not verified, and the formal statement is shown in every result so it can be checked. [The translation step](https://qwedai.com/limits#translation)

[proof\_ref](#proof-ref)

A SHA-256 commitment to the evidence behind a VERIFIED result. It makes any later change to the evidence detectable. It is a record of what was checked, not the proof itself.

[Attestation](#attestation)

A signed token (ES256 JWT) over a result. A signature proves who issued the result and that it was not altered; it does not prove the claim or imply admission. [What a signature proves](https://qwedai.com/limits#signatures)

[Verification Context](#verification-context)

The standard record of a check: what was checked, how, the verdict, the admission decision and the proof\_ref. Specification 1.0, in draft. [Specifications](https://qwedai.com/specs)

[Proof engine](#proof-engine)

An engine that can return VERIFIED, always with a proof\_ref: Math, Logic, SQL, Code and Schema. Symbolic searches for counterexamples and never returns VERIFIED. [Proof engines](https://qwedai.com/engines#proof)

[Policy guard](#policy-guard)

A check that flags unsafe commands, leaked secrets or untrusted tool calls by rule. Guards deny; they never return VERIFIED. [Policy guards](https://qwedai.com/engines#guards)

[Advisory engine](#advisory-engine)

An engine that gives a signal for review, sometimes with a model involved. It never decides; its results are recorded beside the verdict. [Advisory engines](https://qwedai.com/engines#advisory)

[False accept](#false-accept)

A claim that does not hold but was admitted. The one failure fail-closed design cannot catch on its own, so QWED measures it on every release and publishes each case it finds. [Evidence](https://qwedai.com/evidence)