The Principia Machina/Diagrams/03 Digest gate and recovery

Structural diagram 3 of 12. Part of the TPM hub.

• KIND: process
• LANGUAGE: Mermaid flow
• GENERATED FROM: static, TPS 2.5
• STATUS: hand-authored at TPS 0.1.0; superseded by TPX at its first build
• SOURCE SHA-256: 724777babcce12109bade5bab80d0b5b6c570478bcf75947421fc8476aeb3272
• KEY: key for process diagrams: what each shape and arrow means; definition of terms; contents of the specification

Rendered live from the source, which is the text equivalent and is shown under the drawing; a wide drawing scrolls sideways inside its frame.

Source (the text equivalent; Mermaid)

%% 03 Digest gate and recovery. process/Mermaid flow. Generated from: static, TPS 2.5.
flowchart TD
  W[write requested] --> R[TPX recomputes D-TFK and<br/>matches the certificate<br/>2.5.8]
  R -- match --> OK[write proceeds]
  R -- mismatch --> H[write halted;<br/>the mismatched zone named<br/>2.5.5, 2.5.6]
  H --> D[/human declares<br/>RESTORE or FORK<br/>2.5.7/]
  D -- RESTORE --> RS[TFK pages returned to the<br/>revision whose content hash<br/>matches the chain]
  RS --> R2[digest re-verified]
  R2 -- match --> OK
  D -- FORK --> F[COPY-FORWARD under a<br/>newly declared TFK<br/>3.4]

  classDef task fill:#eaecf0,stroke:#a2a9b1,color:#202122
  classDef human fill:#eaf3ff,stroke:#36c,color:#202122
  classDef data fill:#fef6e7,stroke:#ac6600,color:#202122
  classDef bad fill:#fee7e6,stroke:#d33,color:#202122
  classDef good fill:#d5fdf4,stroke:#14866d,color:#202122
  class W,R,RS,R2,F task
  class D human
  class OK good
  class H bad

Text equivalent

Before every write TPX recomputes D(TFK) and matches it against the certificate (2.5.8). A match lets the write proceed. A mismatch halts the write and names the zone (2.5.5, 2.5.6); recovery is a human declaration: RESTORE returns the TFK pages to the revision whose content hash matches the chain and writes resume only after the digest matches; FORK copies forward under a newly declared TFK (2.5.7, 3.4).