GSN V3 Notation Reference
This reference is based on the GSN Community Standard V3 (SCSC-141C), published by the Safety-Critical Systems Club. Features marked as "Planned" in the compliance table below are part of the GSN V3 specification but not yet available in Lemmatica.
Structural elements
Goal
A claim or assertion about the system. Goals are the core building blocks of every safety argument.
- Can have children: Strategy or Solution (not Goal directly)
- Can have annotations: Context, Assumption, Justification
- Special states: Undeveloped (dashed border, no children yet), Away (dashed border, links to sub-case)
Every safety argument has exactly one top-level goal — the overarching safety claim being made.
Strategy
The reasoning approach used to decompose a goal into sub-goals.
- Can have children: Goal only
- Can have annotations: Context, Assumption, Justification
A strategy answers the question: "How are we arguing this goal?" Common strategies include argument by decomposition, argument by evidence type, and argument by hazard classification.
Solution
A reference to evidence that supports a claim.
- Can have children: None (always a leaf node)
- Can have annotations: Context, Assumption, Justification
Solutions point to concrete artifacts: test reports, analysis results, review records, simulation outputs.
Annotation elements
Annotations do not participate in the argument tree hierarchy. They attach to structural nodes to provide additional context.
Context
Scoping information for a claim — definitions, system boundaries, operating conditions.
- Attaches to: Any structural node
Assumption
Something accepted as true without proof within this argument.
- Shape: Oval (ellipse)
- Attaches to: Any structural node
Don't hide assumptions
Hidden assumptions are a leading cause of safety case weaknesses. Making assumptions explicit — even obvious ones — strengthens your argument and makes it easier to review.
Justification
Rationale for why a particular approach is appropriate.
- Shape: Oval (ellipse) with J marker
- Attaches to: Any structural node
Structural rules
| Rule | Description |
|---|---|
| Goals must be developed | A goal must have at least one Strategy or Solution child, or be marked as undeveloped |
| Goals cannot parent goals | A goal cannot directly connect to a sub-goal; a Strategy must mediate |
| Strategies must have goal children | A strategy's children must all be goals |
| Solutions are leaf nodes | A solution cannot have any children |
| Single root | Each document has exactly one top-level goal with no parent |
| No cycles | The argument tree must be acyclic |
Live validation
Lemmatica checks all of these rules continuously as you edit. Violations appear as inline errors on the affected nodes — you don't need to run a separate validation step.
Edge types
Parent-child (SupportedBy)
Structural relationship forming the argument tree:
- Goal → Strategy
- Goal → Solution
- Strategy → Goal
Annotation (InContextOf)
Attaches context, assumptions, or justifications to a structural node. Annotation edges do not form part of the tree hierarchy.
Modular extensions
Away goals
An away goal is a leaf goal that references another document. The referenced document contains the sub-argument that develops this goal.
Away goals enable:
- Decomposition of large arguments into manageable parts
- Reuse of common sub-arguments across multiple safety cases
- Team collaboration where different teams own different sub-cases
Undeveloped goals
A goal marked as undeveloped explicitly signals that the argument below it has not been completed. This is useful for work-in-progress safety cases.
Dialectic extension
Coming soon
The dialectic extension is part of the GSN V3 specification and is on Lemmatica's roadmap. The notation is documented here for reference.
The GSN V3 dialectic extension adds formal counter-argumentation to safety cases.
Challenge
A counter-argument raised against a goal or solution. Challenges question whether a claim is valid or whether evidence is sufficient.
Defeated state
When a challenge is accepted, the challenged node becomes defeated. Defeat propagates upward through the tree — if a child goal is defeated, its parent strategy and parent goal may also be affected.
This mechanism lets teams formally document objections, track their resolution, and make the impact of unresolved challenges visible at every level of the argument.
GSN V3 compliance
Lemmatica implements the GSN Community Standard V3 (SCSC-141C) with the following coverage:
| Feature | Status |
|---|---|
| Core node types (Goal, Strategy, Solution) | Supported |
| Annotation types (Context, Assumption, Justification) | Supported |
| Structural validation rules | Supported |
| Away goals (modular extension) | Supported |
| Undeveloped goals | Supported |
| Dialectic extension (challenges, defeated state) | Planned |
| Argument patterns | Planned |