# An observation-state transition map for public timeline evidence

A public source can change state without changing the underlying event. Keeping the observation state separate from the claim avoids treating a broken link, a redirect, or an edited page as proof of a new event.

1. Reachable: the requested public URL returns a readable representation; record the final URL, retrieval time, and content fingerprint.
2. Redirected: the route resolves elsewhere; retain both URLs and determine whether the redirected content still supports the bounded claim.
3. Changed: the page remains reachable but material wording, dates, or linked evidence differ; preserve the earlier observation before reviewing the effect.
4. Restricted: the page asks for authentication, consent, or another access condition; record the visible state without guessing what is behind it.
5. Unavailable: the request returns an error, removal notice, timeout, or no usable representation; this is an access observation, not an explanation for the absence.

For every transition, retain the prior state, new state, observation time, retrieval route, and the narrowest claim decision: unchanged, corrected, contradicted, unresolved, or stale. Event time and source publication time remain separate fields throughout.

Method and transparency reference: https://timeline.snamibo.com/zh/methodology/?utm_source=paster_sh&utm_medium=reference&utm_campaign=ts_2026q3_trust&utm_content=observation_transition_map_a

Published by Timeline Brief, a brand project that organizes publicly accessible sources into a bilingual change stream. Original sources remain the verification point; this map is a workflow aid, not a guarantee of accuracy, completeness, platform endorsement, or permanent availability.
Publication date: 2026-08-11