Consistency & Reconciliation

Trace a read, preserve concurrent versions, and retain per-key session floors.

Prerequisite: componentwise vector comparison; missing dimensions are zero.

A label has a model boundary

At time 22, visible writes are [1] at 10, then [3,0] and [2,1] at 20. The later equal-time input makes [2,1] latest.

[3,0] with context [1] is causal; [2,0] is invented and takes the fallback. Per-read labels do not certify a concurrent history or eventual convergence.

Eligibility before speed

Latest=100, window=5. Replica 1: applied94/latency2; replica2: applied96/latency12; replica3: applied98/latency12.

Choose 3. Bounded mode orders latency, lag, ID. Fallback orders lag, latency, ID. An overflowing lag stays outside every representable bound.

Concurrent frontier versus LWW

VCs [1,0], [2,0], [1,1] leave the last two as multi-version winners.

LWW is a separate explicit reconciliation policy; a timestamp winner need not dominate causally. Equal VCs plus different payloads survive in the multi-version task.

Never lower a session floor

write7 → write3 → read5 → read2 → write4

First failures: MW=1, RYW=2, MR=3, WFR=4. Keep maximum prior read/write per key. Failed operations do not erase history.

Reconstruct independently

Add [3,1] to the version frontier. Predict survivors before implementing. Then construct a session satisfying RYW but violating MR. Explain what a scalar per-key model cannot say about cross-key dependencies.