canonical-ml — Canonical Merkle Log

Tier L2 — a single-algorithm canonical library. canonical-ml is the append-only engine over the structural Merkle Spine (merkle-spine). It is the append-only peer of the mutable canonical-mt tree; both build on merkle-spine and neither depends on the other. The one currency they exchange is the spine's general structural Seal.

Role

CML (Canonical Merkle Log) owns one algorithm's append-only mechanism:

• Frontier carry — the base-k reduction schedule (the bounded continuation state), itself an optimization of the spine's proof topology.
• The member-root fold — one algorithm's raw root, the fold of its frontier peaks.
• Append-only consistency — the ConsistencyProof (append-only prefix), sound here precisely because the log only ever grows. It is the proof a mutable tree cannot offer.
• Inclusion and leaf proof generation, verified in the spine.
• The structural snapshot facet — the frontier peaks a spine::Seal freezes, and the base case for filling.

Epoch-free and substrate-borrowing

CML is epoch-free and multi-algorithm-free: it reads one algorithm's view over a borrowed node-reader substrate and never owns the store. That is what lets the polydigest combinator drive N CML views over one shared data substrate without duplicating leaf data. The activation timeline, the null-run-extents, the binding root, and coupling are the combinator's facet, not CML's. The structural commitment a CML seal produces is the general spine::Seal; the epoch facet over it is polydigest::BoundSnapshot.

Place in the layered model

merkle-spine  ◄── the structural core
  │
  ├── canonical-ml  ◄── this crate (append-only)
  └── canonical-mt      (mutable)
        │
      polydigest (the combinator that lifts both; polydigest(canonical-ml) is EML)
        │
      EML / EMT / ETL  (k=2 instantiations)

Further reading

• merkle-spine — the structural core this library builds on.
• canonical-mt — the mutable peer; both exchange Seal.
• polydigest — the combinator that lifts canonical-ml to EML with the activation timeline and binding root.
• ../docs/architecture.md — the full design.