3.2 State Transition Monitoring

---
title: "Figure 3.1: State Transition Monitoring Sequence Diagram"
---

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sequenceDiagram
    participant BC as Protocol
    participant PM as Watcher
    participant STD as State Transition Detector
    participant RG as Record Generator

    BC->>PM: Event signal (e)
    PM->>STD: Forward Event signal (e)
    STD->>STD: Reconstruct States (s, s')
    STD->>STD: Compare States (ΔS)
    alt δ ≠ 0
        STD->>RG: Detected State-Transition (e, s, s')
        RG->>RG: Hash(s') for h'
        RG->>RG: Hash(s) for h
        alt h' ≠ h
            RG->>RG: Record State-Transition (e, s, s')
        else h'= h
            RG->>RG: Discard
        end
    else δ = 0
      STD->>STD: Discard
    end

The process follows these steps:

1. Protocol Registration: Protocols are registered with the ASP system, providing their $Scope$ function and event signatures.

2. Event Listening: The Watcher subscribes to signals (event emission) from registered protocols that indicates a state change and forwards the event signal $e$ to the State Transition Detector.

3. State Reconstruction:

   Important

   It is expensive & inefficient for the Observer to reconstruct or store the entire state of the protocol.

   $s$ and $s^{\prime }$ are only state representations / proofs which carry enough information to verify a state-transition with comparator function $\Delta S$.

   For example: $s$ could be a merkle-proof of a state-root, and $s^{\prime }$ could be the new state-root.

   With a well-defined state-space $S$ and state transition-function $T$, $s$ and/or $s’$ is reconstructed from data carried by $e$ and the cached pre-image read from the state-buffer.

4. State Comparison: The $\Delta S$ function is applied to determine if a meaningful state transition has occurred:

   $$\delta =\Delta S(s,s’)$$ Where $\delta \ne 0$ indicates a state transition.

5. Trigger Record Generation: Tuple $(e,s,s’)$ is sent to the Record Generator to compose a cryptographic record of the state transition if $\delta \ne 0$.

6. Record Generation: The Record Generator hashes the new state $s’$ and the previous state $s$ to create a record of the state transition:

   $$R=(Scope,e,h,h’)$$

   Where $h$ and $h’$ are the hashes of the previous and new states and $h\ne h’$.