Title: Goal Structuring Notation (GSN) | ISO 26262 Academy URL: https://iso26262.academy/features/concepts/gsn Description: Build a safety argument in Goal Structuring Notation: core elements and relationships, a construction method, modular arguments and what assessors review. --- Concept guide · GSN Community Standard · 12 chapters # Goal Structuring Notation (GSN) Learn to build safety arguments a reviewer can check: the GSN elements and rules, a construction method, modular and pattern-based arguments, confidence and defeaters, and how reviews find fallacies. 12 Chapters 6 Construction steps 1 Worked EPS argument Included in [Expert](https://iso26262.academy/pricing#plan-advanced) [Preview free](https://iso26262.academy/register?plan=free&from=%2Fconcepts%2Fgsn&utm_source=website&utm_medium=cta&utm_campaign=features_concepts) See the chapters Inside the course 1. 01 **Why Safety Arguments Need Structure** 2. 02 **The Safety Case in ISO 26262** 3. 03 **The Core GSN Elements** 4. 04 **Relationships & Well-Formed Structures** 5. 05 **The Six-Step Method** The short version ## Quick answers What is GSN (Goal Structuring Notation)? GSN is a graphical notation for constructing and presenting safety arguments, defined by the GSN Community Standard. It expresses an argument through six core element types: Goals (claims), Strategies (the inference between claims), Solutions (evidence), plus Context, Assumption, and Justification attached sideways: connected by exactly two relationship types: SupportedBy, which carries the inference, and InContextOf, which scopes it. In automotive use, GSN structures the safety case that ISO 26262-2 requires, connecting lifecycle work products such as HARA results, FMEDA reports, and verification records into an explicit, reviewable argument that the item achieves acceptable safety. Does ISO 26262 require GSN? No. ISO 26262-2 requires a safety case: a compiled argument connecting evidence to the claim of acceptable functional safety, progressively assembled across the lifecycle and checked by a confirmation review whose independence grows with ASIL. The standard does not mandate any notation for that argument. GSN is simply the most widely adopted way to make the argument explicit, because prose safety cases collapse under the volume of work products an ASIL D item generates, hiding gaps that a structured notation exposes. Keep going, free - [Article · 8 min read A Quick Guide to Using GSN for ISO 26262 Safety Cases](https://iso26262.academy/blog/gsn-iso-26262-safety-cases-guide) - [Demo exam · no account Test yourself with 7 exam-style questions](https://iso26262.academy/demo-exam) Why this course · ISO 26262, Part 2 ## Why it pays for itself ### Make safety arguments reviewable Prose buries inference and coverage once an ASIL D item accumulates thousands of work products. GSN makes the claim-argument-evidence chain explicit enough for an assessor to read in minutes. ### Build with the six-step method Kelly's construction loop turns a blank canvas into a well-formed argument and tells you when a branch has reached the right granularity. ### Scale across organizations Modules, away elements, and contracts let one argument span OEM, supplier, and SEooC boundaries, mapping the argument structure directly onto the DIA and distributed development. After the course ## What you’ll be able to do ### Write claims that can be judged Phrase goals as propositions a reviewer can call true or false, with scope fixed by context. ### Build well-formed arguments Use the element types and relationships correctly and construct an argument with a repeatable method. ### Scale arguments across teams Use modules, contracts and patterns to split an argument across suppliers and reuse it safely. ### Argue confidence Show why the evidence deserves trust and deal openly with defeaters and counter-evidence. ### Review an argument Find fallacies and gaps in your own or someone else's GSN before an assessor does. The curriculum · 12 chapters ## Chapter by chapter 1. 01 **Why Safety Arguments Need Structure** See why someone is owed an explicit safety argument, where prose arguments break down, and what GSN is and is not. - Owing an argument - Where prose breaks down - What GSN is 2. 02 **The Safety Case in ISO 26262** Read what the standard asks of a safety case, who consumes it, and how it grows across item, element and supply-chain levels. - What the standard requires - Who reads the argument - A living work product 3. 03 **The Core GSN Elements** Meet every element type, write goals that can be false, make strategies state their inference, and attach context, assumptions and justifications. - Falsifiable goals - Explicit strategies - Undeveloped elements 4. 04 **Relationships & Well-Formed Structures** Use SupportedBy and InContextOf correctly, check connections against the permitted matrix, and recognize the common syntax errors. - SupportedBy and InContextOf - Permitted connections - Common syntax errors 5. 05 **The Six-Step Method** Get past the blank canvas with the six-step construction loop, apply one decomposition level live, and decide when to stop. - Six steps, one loop - Live decomposition - Granularity 6. 06 **Worked EPS Example** Build part of an electric power steering argument phase by phase, see which step produced each node, and leave honest gaps visible. - Item and safety goal - Phase-by-phase fragment - Honest gaps 7. 07 **Modular GSN** Split a large argument into modules with away elements and contracts, and map modules onto DIA and SEooC boundaries. - Modules and away elements - Contracts and interfaces - DIA and SEooC 8. 08 **Patterns & Reuse** Reuse argument structures through pattern notation, tour some illustrative patterns, and instantiate them with the discipline a pattern library needs. - Pattern notation - Illustrative patterns - Instantiation discipline 9. 09 **Confidence & Defeaters** Separate the safety argument from the confidence argument, place assurance claim points, and handle defeaters and counter-evidence. - Assurance claim points - Three kinds of defeater - Counter-evidence 10. 10 **Review & Fallacies** Learn what a GSN review checks, recognize argument fallacies in context, and practice on fragments before running a real review. - Review scope - Fallacy field guide - Spot the fallacy 11. 11 **Tools & Alternatives** Compare GSN with other argument notations, see the SACM metamodel underneath, and pick tooling by what keeps the argument alive. - Notation landscape - SACM metamodel - Tool categories 12. 12 **Pitfalls & Checklist** Review the recurring GSN pitfalls and what a reviewer examines first, then run a self-audit before the argument goes to assessment. - Pitfall field guide - Reviewer first look - Self-audit Read all 12 chapters with Expert. Start with a free account: the complete Functional Safety Concept guide and 5 practice exams a month, then upgrade when you need this guide. [Expert](https://iso26262.academy/pricing#plan-advanced) [Preview free](https://iso26262.academy/register?plan=free&from=%2Fconcepts%2Fgsn&utm_source=website&utm_medium=cta&utm_campaign=features_concepts) [Try the 7-question demo exam](https://iso26262.academy/demo-exam) Interactive figures ## Not just text: the visual toolkit ### Prose versus GSN The same argument written as prose and drawn in GSN, so you can compare what each hides. ### Falsifiability bench Decide whether a statement is a claim at all before it becomes a goal. ### Permitted-connections matrix Which element may connect to which, and with which relationship. ### Assurance claim points Where confidence arguments attach to the EPS safety argument. ### Spot the fallacy Argument fragments to judge before reading the explanation. Worked Example ## An EPS Safety Argument Fragment Chapter 6 builds part of the argument for an electric power steering safety goal and shows which method step produced each node. - The item, the safety goal and the safe state being argued - Which construction step produced which node - The argument fragment assembled phase by phase - Undeveloped goals left visible instead of hidden EPS argument fragment Top goal: the steering assist safety goal is achieved for the fictional EPS item Unlock in course Built for ## Who this guide is for - Safety managers compiling a safety case toward a confirmation review - Engineers who must turn a pile of work products into an explicit argument - OEM and supplier teams splitting a safety case across a DIA boundary - Reviewers and assessors judging whether an argument actually supports its claim ## Frequently Asked Questions Common questions about Goal Structuring Notation (GSN) Goals are propositions a reviewer can judge true or false, not activities or document names. Strategies name the inference used to decompose a goal, such as arguing over each fault class. Solutions are the evidence leaves, citing real work products. The three sideways elements control how the argument reads: Context fixes the meaning and scope of a claim, Assumptions state what is taken as given, and Justifications explain why an approach is adequate. Only ten element-to-element connections are legal, and the permitted-connections matrix decides whether a diagram is even well-formed GSN. The construction method from Tim Kelly's doctoral work at the University of York builds a goal structure top-down: state a claim, fix its context, name a strategy, derive the sub-goals it produces, and repeat until each claim can rest directly on evidence. The value is the discipline it enforces. Every inference is named, every claim has a fixed scope, and decomposition stops at evidence instead of trailing off into branches nobody flagged as undeveloped. The course applies one decomposition level live, then uses the method to build an EPS argument fragment. Twelve chapters covering the core elements and relationships with their well-formedness rules, the six-step construction method, a worked electric power steering argument, modular GSN for distributed development, patterns, confidence arguments and defeaters, review and fallacies, notations and tools, and a closing pitfall guide with a self-audit. A free account starts you off, and the Pro and Expert plans unlock more of the library. ## Writing this for a real project? Have an engineer check your document before the assessor does, or help you write it. From **$790** with a written quote before any charge [See how we can help](https://iso26262.academy/features/consulting?service=work_product#sample) ## Start the course today A free account unlocks one full concept guide, 3 work product templates, 1 guided process, the Markov and RBD simulators, and 5 practice exams per month. The Pro and Expert plans unlock more of the 93-guide library. No credit card required. [Preview free](https://iso26262.academy/register?plan=free&from=%2Fconcepts%2Fgsn&utm_source=website&utm_medium=cta&utm_campaign=features_concepts) [View Pricing Plans](https://iso26262.academy/pricing) Continue with ## Where this topic leads next. [Browse all 93 guides](https://iso26262.academy/features/concepts#library) - Verification and assessment [Proven in Use](https://iso26262.academy/features/concepts/proven-in-use) ISO 26262-8 Clause 14 lets you trade development evidence for statistically demonstrated field experience. This concept shows when that trade actually closes and, far more often, why it does not. [Expert](https://iso26262.academy/pricing#plan-advanced) 11 chapters - Verification and assessment [Change Impact Analysis for Carryover & Modified Systems](https://iso26262.academy/features/concepts/change-impact-analysis) Most automotive projects reuse existing systems. This page shows how ISO 26262 impact analysis and Part 8 Clause 8 change management decide what stays valid, what must be re-verified, and how to keep carryover, variants, and facelifts safe. [Expert](https://iso26262.academy/pricing#plan-advanced) 10 chapters - Vehicle domains [Actuator Safety](https://iso26262.academy/features/concepts/actuator-safety) Motors, valves and relays are where safety goals become physical: learn how actuation channels fail stuck or runaway, how feedback and diagnostics catch it, and how safe states from de-energize to active hold are engineered and quantified. [Expert](https://iso26262.academy/pricing#plan-advanced) 14 chapters