{"name":"ProductKnowledgeGraph evidence methodology","version":"1.0","updated":"2026-09-21","url":"https://productknowledgegraph.com/evidence","levels":[{"id":"P0","name":"Published","definition":"A stable URL answers with a content type, a timestamp and a hash."},{"id":"P1","name":"Accessible","definition":"External HTTP access without authentication and without client-side rendering."},{"id":"P2","name":"Crawled","definition":"A crawler requested a specific resource, and the request was checked against the provider's published ranges or reverse DNS."},{"id":"P3","name":"Retrieved","definition":"A resource fetch is traceable to a user-triggered query."},{"id":"P4","name":"Cited","definition":"An observed AI answer contains the URL."},{"id":"P5","name":"Fact matched","definition":"An answer reproduces a versioned, source-backed value from the record."},{"id":"P6","name":"Answer influenced","definition":"A controlled experiment with one changed factor supports causal influence."}],"notInferred":["A higher level is never inferred from a lower one.","A crawler visit is not retrieval; retrieval is not citation; a citation is not use of a fact.","A user agent string is a claim, not an identity: an unverified request is recorded as unverified, never as a provider visit.","An observation without the provider, the exact model name and the date is not evidence and is not stored as one.","No level, alone or combined, supports a statement about a lost sale, a ranking or revenue."],"changelog":[{"version":"1.0","date":"2026-09-21","change":"First versioned publication. The seven levels were in use from 26.07.2026; this fixes their wording and publishes them as JSON."}]}