A state letter is a compressed statement about permissions and data responsibility. Start with the invariants, then derive why MSI needs three states and what E and O add. Finally ask how the system discovers other copies and orders their requests. Read Why Coherence Exists first if exclusive holders and dirty responsibility are unfamiliar.
Lesson | After it you can... |
|---|---|
Recognize legal reader/writer permission combinations. | |
Spot wrong values even when state permissions look legal. | |
Explain two policies without mixing their message contracts. | |
Find the first incorrect permission or lost value. | |
Connect states to processor events, forwarded requests and invalidations, and actions. | |
Explain why a clean exclusive holder can store silently. | |
Distinguish dirty responsibility from write permission. | |
Record the work still required before a permission grant. | |
Explain what the ordered broadcast contributes. | |
Track possible holders without treating metadata as data. | |
Compare discovery, ordering, traffic and storage assumptions. | |
Explain safe conservative filtering and its limits. |
The invariants specify what must remain true. The transition rules implement those obligations across incoming events, outgoing messages and intermediate states. Naming an invariant alone does not show a controller preserves it.