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GSN Safety Case Overview

Saphira automatically generates Goal Structuring Notation (GSN) safety cases that demonstrate your system meets safety requirements through structured Goal → Strategy → Evidence chains—required for Proof of Validity (PoV) acceptance and regulatory approval.

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GSN Node Types

High-level safety claims to be demonstrated:
  • Root goal: Overall system safety claim
  • Sub-goals: Decomposed safety objectives
  • Clear, measurable safety statements
Example: “G1: The system is safe and reliable in all operational conditions”
How goals are argued to be satisfied:
  • Argument approaches and methodologies
  • Decomposition rationale
  • Evidence grouping logic
Example: “S1: Argue based on hazard analysis and mitigation coverage”
Specific evidence supporting the argument:
  • Requirements that address safety
  • Test results and analyses
  • Design documentation
  • Certification artifacts
Example: “SOL1: REQ-SAFETY-001 - Emergency stop response ≤500ms”
Key assumptions underlying the safety argument:
  • Operational assumptions
  • Environmental assumptions
  • User behavior assumptions
  • System boundary assumptions
Example: “A1: Operators are trained per procedure OPS-001”
Types of evidence required to support claims:
  • Test reports
  • Analysis results
  • Certifications
  • Verification activities
Example: “E1: HIL test report demonstrating fault detection”
Contextual information for the argument:
  • System description
  • Operational domain
  • Applicable standards
  • Scope boundaries
Example: “C1: Automotive brake system operating on public roads”

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Goal → Strategy → Evidence Chains

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Complete Argument Structure

Saphira builds complete argument chains from your project data: 
┌─────────────────────────────────────────────────────────────┐
│                    G1: Root Safety Goal                      │
│  "The system is acceptably safe for its intended use"       │
└─────────────────────────────────────────────────────────────┘
                              │
          ┌───────────────────┼───────────────────┐
          ▼                   ▼                   ▼
    ┌──────────┐        ┌──────────┐        ┌──────────┐
    │ S1: Argue │        │ S2: Argue │        │ S3: Argue │
    │ by hazard │        │ by design │        │ by V&V    │
    │ coverage  │        │ controls  │        │ evidence  │
    └──────────┘        └──────────┘        └──────────┘
          │                   │                   │
    ┌─────┴─────┐       ┌─────┴─────┐       ┌─────┴─────┐
    ▼           ▼       ▼           ▼       ▼           ▼
┌───────┐ ┌───────┐ ┌───────┐ ┌───────┐ ┌───────┐ ┌───────┐
│ SOL1  │ │ SOL2  │ │ SOL3  │ │ SOL4  │ │ E1    │ │ E2    │
│ HAZ-1 │ │ HAZ-2 │ │ REQ-1 │ │ REQ-2 │ │ Test  │ │ Cert  │
└───────┘ └───────┘ └───────┘ └───────┘ └───────┘ └───────┘

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Argument Strategies

Argue safety through hazard mitigation:
  • All hazards identified
  • Each hazard has mitigating controls
  • Controls verified effective
  • Residual risk acceptable
Argue safety through design measures:
  • Requirements address safety
  • Design implements requirements
  • Architecture provides redundancy
  • Fault tolerance demonstrated
Argue safety through V&V evidence:
  • Test plans cover safety requirements
  • Tests executed successfully
  • Independent verification performed
  • Compliance demonstrated
Argue safety through standards adherence:
  • Applicable standards identified
  • Clauses addressed
  • Evidence documented
  • Conformity demonstrated

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GSN Generation Workflow

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From Project Data

Saphira collects your safety artifacts:
  • Requirements database
  • HARA hazards and controls
  • FMEA failure modes
  • Test results and evidence
  • Standards compliance status
AI generates the safety argument:
  • Root goal from system description
  • Strategies from analysis types
  • Solutions from requirements
  • Assumptions from project context
  • Evidence links from test results
Edit the generated safety case:
  • Adjust goal wording
  • Add/remove strategies
  • Link additional evidence
  • Document assumptions
  • Add contextual information
Verify safety case integrity:
  • All goals supported by strategies
  • All strategies have solutions/evidence
  • No orphan nodes
  • Traceability complete
  • Gaps identified
Generate documentation:
  • GSN diagram (visual)
  • YAML/JSON structure
  • PDF report
  • Presentation format

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GSN Wizard

For guided safety case creation:
The GSN Wizard asks structured questions:System Context:
  • System name and purpose
  • Operational domain
  • User types and assumptions
Hazard Identification:
  • Known hazards
  • Mitigation strategies
  • Risk assessment approach
Safety Requirements:
  • Safety function definitions
  • Performance requirements
  • Architectural elements
Verification Approach:
  • Verification methods
  • Test coverage
  • Evidence types
Standards Compliance:
  • Applicable standards
  • Compliance status
  • Certification targets
From wizard answers, Saphira generates:
  • Root goal using system name and purpose
  • Strategies addressing specific hazards
  • Solutions mapping wizard answers
  • Assumptions from operational context
  • Evidence requirements from verification strategy
Each GSN node includes:
  • wizard_links: Question IDs that informed the node
  • external_links: External references from answers
  • requirement_ids: Linked requirements
  • hazard_ids: Related hazards
  • test_ids: Associated tests

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Evidence Mapping

GSN nodes link to:
  • Test reports from verification
  • Analysis documents from assessments
  • Certifications from third parties
  • Design specifications from requirements
Saphira identifies:
  • Goals without sufficient evidence
  • Strategies without solutions
  • Missing assumptions
  • Incomplete argument chains

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Industry Templates

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Automotive Safety Case (ISO 26262)

Structure aligned with ISO 26262-10:
  • Item definition goal
  • HARA completeness argument
  • Safety concept adequacy
  • Verification evidence
  • Confirmation measures

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Industrial Safety Case (IEC 61508)

Structure for SIS justification:
  • Safety function goals
  • SIL allocation argument
  • Architecture adequacy
  • Validation evidence
  • Lifecycle compliance

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Autonomous Systems (UL 4600)

Structure for autonomous systems:
  • ODD definition completeness
  • Safety performance targets
  • Development process adequacy
  • Verification coverage
  • Field monitoring plan

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Export Formats

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GSN Diagram Export

  • SVG/PNG: Visual GSN diagram
  • Mermaid: Embeddable diagram code
  • Draw.io: Editable diagram format

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Structured Export

  • YAML: Machine-readable structure
  • JSON: API integration format
  • XML: Standards-based exchange

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Documentation Export

  • PDF: Formatted safety case report
  • Word: Editable document
  • HTML: Web-viewable format

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Validation Features

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Completeness Checking

Saphira validates:
  • All goals have supporting strategies
  • All strategies have evidence or sub-goals
  • No orphan nodes in structure
  • Required assumptions documented
  • Evidence references valid

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Argument Strength Analysis

Assessment of:
  • Evidence quality ratings
  • Assumption validity
  • Traceability completeness
  • Gap severity levels

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Integration with Saphira Workflows

GSN safety cases integrate with:
  • Requirements: Goals trace to requirements
  • HARA: Hazards become evidence for hazard coverage arguments
  • FMEA: Failure modes support failure analysis arguments
  • Tests: Test results become evidence nodes
  • Standards: Clause compliance supports standards arguments
  • Gap Analysis: Gaps become undeveloped goals or missing evidence