Summary

Protocol upgrade from v7.3 to v7.4 in response to an external deep dive review of the Railway Signalling System report. The review identified structural gaps that exist systemically across projects. This update fixes the railway project and adds protocol rules to prevent recurrence.

Deep Dive Review

An independent review of the Railway Signalling System decomposition report assessed the autonomous output against real systems engineering standards. The report covers an 11-subsystem CENELEC-compliant mainline signalling system with 240 requirements, 134 relationships, and 13 architecture diagrams.

Strengths identified

• Decomposition boundaries align with established UK signalling domain practice (GRIP Stage 3/4)
• Requirements are quantitative and well-rationalised with EARS compliance
• Verification plan includes negative testing, statistical rigour, environmental extremes, and endurance testing
• Traceability chain is structurally sound with meaningful derivation descriptions
• UHT classification reveals genuine cross-domain architectural patterns

Gaps identified

Finding	Severity	Action
Zero stakeholder requirements (broken derivation chain)	CRITICAL	Protocol + railway fix
~15-20% SUB reqs without verification procedures	HIGH	Protocol + railway fix
Orphan test entities (diesel generator, traffic light)	HIGH	Railway fix (deleted)
No system-level integration tests	HIGH	Protocol
ARC decisions not traced to SYS/SUB requirements	MEDIUM	Protocol + railway fix
Missing internal diagrams (2 subsystems)	MEDIUM	Protocol + railway fix
No hazard log cross-references	MEDIUM	Noted for future

Changes

Railway Signalling Project fixes

1. Deleted 2 orphan test entities from SE:railway-signalling namespace — diesel generator and traffic light controller were created during CLI testing, not real system components
2. Set project to in-progress with REVIEW_NOTES detailing all 5 priority findings for the bot to address
3. Queued as current project — next autonomous session will work on creating STK requirements, completing verification coverage, adding integration tests, tracing ARC decisions, and adding missing diagrams

Protocol v7.4 rules

Rule	Flow	Description
STK requirements mandatory	Flow A step 10	Every system MUST have minimum 3 stakeholder requirements before system requirements. No traceable foundation without them.
System-level integration test	Flow B step 6a	At least one end-to-end test exercising the full input→processing→output chain per system
Verification coverage gate	Flow C step 3	>90% of SUB+IFC requirements must have VER entries before marking qc-reviewed
ARC traceability	Flow C step 4	Every ARC decision must trace to a SYS/SUB requirement or be tagged informational
Orphan entity cleanup	Flow C step 4	Query entities not in any PART_OF relationship; remove test entities, integrate real ones
Diagram completeness	Flow E step 2	Every subsystem must have an internal architecture diagram; flag missing ones

Review verdict (quoted)

“This is a remarkably comprehensive systems engineering artefact for an autonomously generated output. The decomposition is domain-appropriate, the requirements are quantitative and well-rationalised, the verification plan includes genuine negative testing and statistical rigour, and the traceability chain is structurally sound. […] It produces outputs that are recognisably in the same form and at a comparable level of detail to what a team of signalling systems engineers would produce in GRIP Stage 3/4 for a UK mainline resignalling project.”

Implications

1. From session 312 onward, all new systems must have STK requirements and system-level integration tests.
2. The railway signalling system will be reworked to address all review findings before completion.
3. The review document is stored at /docs/Railway-Signalling-Deep-Dive-Review.docx.
4. Protocol version is now 7.4.

Version manifest

Component	Version	Notes
Session protocol	7.4	Up from 7.3
Flow A	+STK mandate	Minimum 3 STK requirements
Flow B	+integration test	End-to-end system test
Flow C	+verification gate, +ARC trace, +orphan check	Three new QC checks
Flow E	+diagram completeness	Final review check