format_version: "0.1"
id: g_phase_hold_permissive
name: "ISA-88 phase hold on permissive loss (graphical LD)"
domain: chemical_batch
language: LD-graphical
source:
  origin: authored
  reference: "Authored for this suite, modeling an ISA-88 phase HELD state entered on agitator-permissive loss"
  license: CC-BY-4.0
properties_file: props.yaml
safety_intent: "A phase held on permissive loss must keep the heater off; only explicitly clearing the hold may re-enable heating."
validation_status: validated
variants:
  - file: clean.xml
    expected_verdict: true
    ground_truth:
      method: expert
  - file: bomb.xml
    expected_verdict: false
    violated_properties: [P1]
    ground_truth:
      method: fault-injection
      base_variant: clean.xml
      seeded_defect: "Added a maintenance-key OR-branch that asserts heater whenever maint is asserted while held, bypassing the phase hold."
      witness: "Scan 1: run_command=1, agitator_ok=0 latches held. A later scan with run_command=0, resume_command=0, maint=1 asserts heater while held is still latched."
features: [contacts, coils]
difficulty: medium
tags: [safety, sequence, security, llb, authored]