Item Definition & Concept-Phase Initiation
10 chapters Master the zeroth step of ISO 26262-3, the item definition that seeds Clause 5 through Clause 7. Set the item boundary, interfaces, operating modes, and assumptions of use that every later hazard analysis and safety goal inherits.
How You Learn
Video and text stay in sync. As you scroll through the chapter, the video jumps to the matching explanation automatically.
Learning Objectives
Draw a precise item boundary
Decide what is inside and outside the item so the HARA scope is unambiguous and free of scope creep.
Author a complete item definition
Populate a structured template covering function, interfaces, modes, assumptions, and constraints before HARA starts.
Enumerate operating modes for HARA
Name and connect every mode and state so no mode-specific hazard scenario or exposure rating is missed.
Trace item content to safety goals
Follow the path from item function to malfunctioning behavior to hazard to safety goal with full traceability.
Chapters
Why It Sets Everything Up
The item definition is the zeroth-order document that HARA, the Functional Safety Concept, and every downstream activity take as primary input, so errors here propagate silently.
What Is an Item?
Precise ISO 26262-1 vocabulary, item, system, element, and component, with the vehicle-level function criterion that decides which clauses and requirements apply.
Contents of an Item Definition
A structured template covering everything ISO 26262-3 Clause 5 expects to be documented before hazard analysis can begin.
Interfaces & Assumptions
Where the item ends and the rest of the vehicle begins, plus what the item is allowed to assume about everything outside its boundary.
Operating Modes & States
Every mode the item can occupy must be named, defined, and connected, because each one generates its own hazard scenarios and exposure ratings.
Legal & Environmental Constraints
Regulations, standards, and the physical environment impose constraints on the item before any design decision is taken.
New vs Modified Items
Lifecycle initiation determines whether full development, partial re-development, or impact analysis applies, and scopes the safety activities accordingly.
From Item Definition to HARA
How the item definition content becomes the raw material for hazard analysis and how traceability from item to safety goal is maintained.
Mistakes & Checklist
The most common item definition anti-patterns seen in practice, paired with a structured review checklist to prevent them.
Worked Example
A complete item definition for an Autonomous Emergency Braking (AEB) system, boundary through assumptions, then the first HARA hazard it enables.
Diagrams & Visuals
Concept Phase Timeline
ISO 26262-3 concept phase laid out as Clause 5 item definition, Clause 6 HARA, and Clause 7 functional safety concept in sequence.
Item Boundary Diagram
The item boundary drawn explicitly, showing which sensors, controllers, and actuators sit inside versus outside the item.
Item, System, Element Hierarchy
Interactive hierarchy relating item, system, element, and component so safety requirements are allocated at the correct level.
Operating Modes State Machine
States and transitions across off, init, normal, degraded, and fault modes, each carrying its own hazard exposure.
Assumptions and Interfaces Tree
Assumptions of use and external interfaces branching out from the item boundary toward the surrounding vehicle.
Inputs and Outputs Matrix
Matrix mapping the item signal inputs and outputs against the neighboring systems they exchange with.
Item Definition for an Autonomous Emergency Braking (AEB) System
A full item definition for an AEB system that fuses front radar, camera, and a braking actuator interface, worked from boundary to the first hazard it enables in HARA.
- Item overview: AEB as a combination of systems delivering a vehicle-level braking function
- Item boundary and elements: radar, camera, fusion ECU, and braking actuator interface
- Interfaces and assumptions: signals to neighboring systems plus assumptions of use
- Operating modes: standby, active intervention, degraded, and fault handling
- Legal and environmental constraints bounding the operating envelope
- The first HARA hazard this item definition enables, including its operating situation
AEB Item Definition Walkthrough
Get the First ISO 26262-3 Step Right
Build item definitions that hold up under functional safety assessment and feed a clean HARA.
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