The rule that makes the ACI standard safe to build on: it grows only by accretion — you add a new member, you never revise a sealed one. Prior art can never break under you, because the past is never rewritten. Watch the family grow outward like tree-rings. Try to revise the core, and the standard refuses — it forks instead, and every old seal still holds.
ACI · a CORE rule made hands-on — extensible by accretion, never by revision
The family, ring by ring · add, or try to revise
Two layers, honestly
Real
The data model is genuinely append-only. Each ring is sealed with a deterministic hash of its content at birth. “Add” pushes a new outer ring and touches nothing inner — press “verify” after any growth and every prior seal still recomputes green. “Revise” is structurally refused: it cannot mutate a sealed ring, so it forks a new one (the old ring stays, sealed, intact). Growth never invalidates the past — that is the property, and it is enforced, not promised.
Figure
The tree-rings are the image (a coral, a trunk — things that only accrete outward). And the seal here is a short demonstration hash, not the full .dlw SHA-256 of the sealing bench; the mechanism (seal-at-birth, never-mutate) is the real content.