Anomalies

Honest by Construction

Read values, final state, serial baseline, and anomaly labels are recomputed before rendering.

highlighted = computed this step

Honest by construction

The author supplies an operation trace and optional expected facts. The engine recomputes read values, final state, serial baseline, and anomaly label before rendering. Note: expected facts can reject a mismatch but cannot create the answer.

recompute boundary\text{recompute boundary}

Compiled trace

The recomputed trace has 1 read and 1 final-state item. Note: the anomaly label is rendered from those facts.

reads=1,final items=1\text{reads}=1,\quad \text{final items}=1

these traces model specific anomalies under a read-latest-write execution model; isolation levels (RC/RR/SI/serializable) and MVCC mechanism are modelled later - no product claims.

Honest anomaly T1 T2 0 W(X,200) 1 R(X)=200 2 abort anomaly: dirty_read final: X=100 serial: X=100

Wrong anomaly reject

A wrong expected anomaly is rejected during the lesson self-test. Note: the rejection happens before any lesson can publish an inconsistent diagram.

reject mismatch\text{reject mismatch}

Summary

Isolation anomaly lessons are honest because read values and labels are recomputed from the trace. Note: isolation levels, serializable behavior, and MVCC mechanisms are deferred to later books.

honest traces\text{honest traces}