Title: Item Definition & Concept-Phase Initiation | ISO 26262 Academy URL: https://iso26262.academy/features/concepts/item-definition-concept-phase Description: Item definition under ISO 26262-3: set the boundary, interfaces, operating modes and assumptions that HARA, safety goals and the safety case build on. --- Concept guide · ISO 26262-3 §5 · 10 chapters # Item Definition & Concept Phase Learn to write the item definition that every later safety activity inherits: boundary, interfaces, assumptions, operating modes and constraints, ready for the HARA. 10 Chapters 3 Development pathways 1 Worked AEB item definition Included in [Expert](https://iso26262.academy/pricing#plan-advanced) [Preview free](https://iso26262.academy/register?plan=free&from=%2Fconcepts%2Fitem-definition-concept-phase&utm_source=website&utm_medium=cta&utm_campaign=features_concepts) See the chapters Inside the course 1. 01 **Why It Sets Everything Up** 2. 02 **What Is an Item?** 3. 03 **Contents of an Item Definition** 4. 04 **Interfaces & Assumptions** 5. 05 **Operating Modes & States** The short version ## Quick answers What is an item definition in ISO 26262? The item definition is the first work product of the ISO 26262 safety lifecycle, required by ISO 26262-3, Clause 5. It describes the item (a system or combination of systems implementing a function at the vehicle level) before any safety analysis begins: its functionality, boundary and interfaces, operating modes and states, assumptions of use, preliminary architecture, and the legal and environmental constraints it must satisfy. Every downstream activity inherits it: the HARA derives hazards from its functions and modes, the functional safety concept builds on its boundary, and the safety case traces back to it. Errors here propagate silently, which is why it deserves a formal review before HARA starts. What is the difference between an item, a system, and an element in ISO 26262? The vocabulary comes from ISO 26262-1 and the distinctions carry real consequences. An item implements a function at the vehicle level: that vehicle-level function criterion is what separates items from everything else. A system, as the standard uses the word, joins at least three kinds of part, one that senses, one that decides and one that acts; an element is a system or part of one, down to components, hardware parts, and software units. Because an item is defined by its vehicle-level function, a Safety Element out of Context (SEooC), developed without knowing the vehicle, can never itself be an item. Keep going, free - [Demo exam · no account Test yourself with 7 exam-style questions](https://iso26262.academy/demo-exam) Why this course · ISO 26262, Part 3, Clause 5 ## Why it pays for itself ### Set an unambiguous HARA scope The item boundary decides what the hazard analysis covers. Learn to draw it explicitly (which sensors, controllers, and actuators are in, which are out) so the HARA starts clean. ### Author a complete item definition A structured template covers functions, interfaces, operating modes, assumptions of use, and legal and environmental constraints: everything ISO 26262-3 Clause 5 expects documented before hazard analysis can begin. ### Catch errors while they are cheap Defects cost roughly 1x at requirements and 10x to 100x at integration. Boundary mistakes and undocumented assumptions propagate silently into ASIL and safety-goal gaps downstream. After the course ## What you’ll be able to do ### Define a clear item boundary State what is inside the item, what is outside and which interfaces cross the line. ### Write a complete item definition Cover functions, modes, assumptions and constraints in a structure reviewers recognize. ### Choose the development pathway Decide between new development, modification and reuse, and justify the choice. ### Hand a clean input to the HARA Give the hazard analysis the functions and modes it needs to derive malfunctioning behavior. ### Review before the gate Catch the anti-patterns that propagate silently into ASILs and safety goals. The curriculum · 10 chapters ## Chapter by chapter 1. 01 **Why It Sets Everything Up** See how the item definition seeds the whole safety lifecycle, how its errors propagate through the V-model, and what late discovery costs. - Foundation of the lifecycle - Error propagation - Cost of late discovery 2. 02 **What Is an Item?** Work through the ISO 26262-1 vocabulary, the vehicle-level function criterion, and how an item differs from an SEooC or a combination of systems. - Vocabulary - Vehicle-level function - Item versus SEooC 3. 03 **Contents of an Item Definition** Learn what ISO 26262-3 asks for, structure it with a template, and judge whether the definition is ready for the HARA. - What Part 3 requires - Structured template - HARA readiness 4. 04 **Interfaces & Assumptions** Define the system boundary, the interfaces to other items, assumptions of use and preliminary architectural assumptions. - System boundary - Interfaces to other items - Assumptions of use 5. 05 **Operating Modes & States** Capture the modes and transitions the HARA needs and see how each mode changes the exposure to a hazard. - Mode taxonomy - State transitions - Modes and exposure 6. 06 **Legal & Environmental Constraints** Record the regulatory frameworks, environmental operating conditions and foreseeable misuse that bound the item. - Regulatory frameworks - Environmental conditions - Foreseeable misuse 7. 07 **New vs Modified Items** Make the lifecycle initiation decision, choose between the development pathways, and scope a modification with an impact analysis. - Lifecycle initiation - Development pathways - Impact analysis 8. 08 **From Item Definition to HARA** Use the item definition as HARA input, derive malfunctioning behaviors, and keep traceability from item to hazard to safety goal. - HARA input - Malfunctioning behaviors - Traceability 9. 09 **Mistakes & Checklist** Recognize the anti-patterns that weaken item definitions and review a draft before it is handed to the HARA team. - Anti-patterns - Review checklist - Good practice 10. 10 **Worked Example** Build an item definition for an automatic emergency braking system, from boundary and modes to the first hazard it enables. - AEB item overview - Boundary and elements - First HARA hazard Read all 10 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%2Fitem-definition-concept-phase&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 ### Item, system, element, SEooC The four terms that look interchangeable and are not. ### Item boundary Move the boundary and watch parts cross in and out of scope. ### Assumptions of use tracker Follow each assumption from stated to mitigated. ### Operating mode state machine Drive the modes of a steering item with events. ### Same malfunction, different ASIL How the operating mode changes the rating of one malfunction. Worked Example ## AEB Item Definition The final chapter writes an item definition for an automatic emergency braking system and follows it to the first hazard the HARA can derive. - Item overview and the vehicle-level function - Boundary, elements and interfaces - Assumptions and operating modes - The first HARA hazard this definition makes possible AEB item definition Item: automatic emergency braking, defined at vehicle level Unlock in course Built for ## Who this guide is for - Engineers kicking off safety work for a new E/E vehicle function - OEM concept teams preparing the inputs a HARA workshop needs - Suppliers verifying the boundary and assumptions a customer item definition hands them - Reviewers gating whether the concept phase is actually ready to start ## Frequently Asked Questions Common questions about Item Definition & Concept Phase The structured template the course teaches covers: the item's functions and their dependencies; the boundary with its elements and interfaces to other items and the wider vehicle; assumptions of use and preliminary architectural assumptions; every operating mode and state, from off and init through normal, degraded, and fault; legal and regulatory requirements; environmental constraints such as temperature, EMC, and vibration; and reasonably foreseeable misuse. A readiness checklist then gates the start of the HARA, if modes are missing or assumptions undocumented, the hazard analysis will inherit the gaps. Lifecycle initiation decides which of three pathways applies: full new development, modification of an existing item, or reuse assessed through an impact analysis. For a modified item, the impact analysis scopes exactly which safety activities must be repeated: a well-bounded modification with documented history may re-run only part of the lifecycle, while an unclear one forces full re-development. Getting this decision documented and justified matters, because it determines the entire safety workload and is one of the first things an assessor examines. Ten chapters covering why the item definition sets up everything after it, the item, system and element vocabulary, the contents template, interfaces and assumptions, operating modes, legal and environmental constraints, the new-versus-modified decision, the handoff into the HARA, and the common anti-patterns with a review checklist. The worked example builds an item definition for an automatic emergency braking system, through to the first HARA hazard it enables. 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%2Fitem-definition-concept-phase&utm_source=website&utm_medium=cta&utm_campaign=features_concepts) [View Pricing Plans](https://iso26262.academy/pricing) Continue with ## Where this topic leads next. 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