ISO 26262 Hierarchical Components - A Software Perspective

ISO 26262 Hierarchical Components - A Software Perspective

Introduction:

The hierarchy in ISO26262 based design begins from the Concept Phase. At every part the components are broken down further to reach the lowest unit of implementation. 

For example the lowest unit for Software are the functions while that of the hardware are hardware components like resistors, capacitors etc.

In the below section the hierarchical components are explained in details from software perspective.The probable ID of each blocks are also suggested so that they can be linked and tracked upstream and down stream.

The basic hierarchy for deriving the SW architecture modules is shown as below.

Phase wise distribution of components:

ISO Part	Section No.	Work product details	Description
Part 3: Concept Phase	3.5	Item Definition	Define the Item at the vehicle level
Part 4: Product development at the system level	4.6	Specification of technical safety requirements	Define the System Level Elements, which can be Hardware (HW) Elements, Software (SW) Elements or Firmware (FW) Elements
	4.7	System design
Part 6: Product development at the system level	6.7	Software architectural design	Each Software (SW) Elements or Firmware (FW) Elements is divided into ·         Software Component (SWC) ·         Software Sub-Component (SSWC) ·         Firmware Component (FSWC) ·         Firmware Sub-Component (FSWC) Each SWC or FWC is further divided into ·         Software Functionality (SF) ·         Firmware Functionality (FF)
	6.8	Software unit design and implementation	Each Software Functionality (SWF) or Firmware Functionality (FWF) is divided into ·         Software Unit functions (SUF) ·         Firmware Unit functions (FUF)

Concept, System Level Hierarchy:

Basic structure:

Example:

Software Level Hierarchy:

Basic structure: