IEC TR 61508-3-3-2025 PDF

Full title and description

Functional safety of electrical/electronic/programmable electronic safety-related systems - Part 3-3: Object-oriented software in safety-related systems. This IEC Technical Report proposes topics, methods and techniques for using object‑oriented (OO) software in safety‑related E/E/PE systems to reduce systematic faults to levels required by IEC 61508 and to justify OO design choices in safety cases.

Abstract

IEC TR 61508-3-3:2025 is a guidance document that supplements IEC 61508‑3 by addressing the specific concerns and recommended practices when object‑oriented languages and techniques are used in safety‑related software. It discusses issues such as dynamic objects, memory allocation, predictable timing, modularization, information hiding and verification approaches that help demonstrate adequate reduction of systematic faults for safety applications. The TR is intended to be read in conjunction with IEC 61508‑3 and does not replace the normative requirements of that part.

General information

• Status: Current / Published.
• Publication date: 16 July 2025.
• Publisher: International Electrotechnical Commission (IEC) — Technical Report (TR).
• ICS / categories: 13.110; 25.040.40 (industrial process measurement and control).
• Edition / version: Edition 1.0 (2025).
• Number of pages: 52 pages (PDF).

Scope

This Technical Report provides guidance on applying object‑oriented software techniques in safety‑related E/E/PE systems within the IEC 61508 framework. It identifies OO‑specific risks (for example dynamic allocation, polymorphism, inheritance complexity, run‑time type issues and timing/predictability concerns) and recommends methods and techniques — including design rules, verification approaches and documentation practices — to control systematic faults to meet the systematic capability required by the applicable safety integrity level. The TR is explicitly a supplement and must be used together with the normative provisions of IEC 61508‑3.

Key topics and requirements

• Overview of OO language features relevant to functional safety (classes/objects, inheritance, polymorphism, dynamic allocation, exceptions) and their safety implications.
• Recommended design techniques to limit systematic faults (e.g., restricted language subsets, safe coding patterns, controlled use of dynamic features).
• Guidance on modularization, information hiding, low coupling and high cohesion for OO architectures in safety contexts.
• Verification and validation strategies adapted for OO software (unit and integration testing, formal methods where applicable, code review focus areas).
• Considerations for timing, memory management and determinism when using OO languages in hard or soft real‑time safety functions.
• Instructions on documenting safety justification and evidence when OO techniques are used, to support assessors and certification activities.

Typical use and users

Used by software engineers, system architects, functional safety engineers, assessors and certification bodies involved in safety‑related E/E/PE systems where object‑oriented languages or techniques are considered. It is also a reference for project managers, procurement teams and regulators who need to understand how OO approaches may be justified within an IEC 61508 safety case.

Related standards

IEC TR 61508‑3‑3:2025 is a supplement to IEC 61508‑3 and should be read alongside the rest of the IEC 61508 series (parts 1–7). It is relevant to sector‑specific functional safety standards (for example IEC 61511 for process industry, ISO 26262 for automotive, EN 13849 / ISO 13849 family for machinery safety) where OO software practices need to be reconciled with sector requirements. It also links to guidance on software lifecycle and assessor involvement in IEC 61508‑3.

Keywords

functional safety, IEC 61508, object‑oriented software, OO, safety‑related software, software lifecycle, systematic faults, verification, safety case, deterministic behaviour.

FAQ

Q: What is this standard?

A: IEC TR 61508‑3‑3:2025 is a Technical Report from the IEC that gives guidance on the safe use of object‑oriented software techniques in safety‑related E/E/PE systems; it supplements the normative requirements of IEC 61508‑3.

Q: What does it cover?

A: It covers OO language features and their safety implications, recommended design and coding practices, verification and validation approaches tailored to OO designs, timing and memory considerations, and documentation needed to justify OO choices in a safety case.

Q: Who typically uses it?

A: Software developers, system and safety engineers, assessors, certification bodies and teams responsible for producing safety cases where OO software is used. Procurement and compliance staff may also reference it.

Q: Is it current or superseded?

A: It was published on 16 July 2025 and is current; the IEC webstore records a stability date indicating it is expected to remain valid through the indicated stability period. Users should always verify for any later amendments or revisions.

Q: Is it part of a series?

A: Yes — it is a Technical Report within the IEC 61508 series (functional safety of E/E/PE systems) and is explicitly intended to be used together with IEC 61508‑3 (software requirements) and the other parts of IEC 61508.

Q: What are the key keywords?

A: Object‑oriented, software safety, IEC 61508, software lifecycle, deterministic timing, memory management, systematic fault reduction, verification, safety case.