About 81346-2

IEC 81346-2:2019 establishes classification schemes with defined object classes and their associated letter codes, and is primarily intended for use in reference designations and for designation of generic types.
The classification schemes are applicable for objects in all technical disciplines and all branches of industry.

The recently updated edition of the standard (IEC 81346:2019) is the result of extensive work by IEC and ISO to update the standard to make it applicable in a broader set of industries, and to provide users with the option of applying more detailed classification when creating reference designations.

The updated and new classification schemes are now based on the rules given in ISO 704, which means that the classification now consists of clearly defined classes of objects that provide a 100% stable classification through the entire object life-cycle.

We believe the new edition is very useful, and therefore would like to introduce you to part of it in brief here.

Entry classes

The classification scheme for technical objects has 17 entry classes in total, identified by the following letter codes:

 Class codeClass definitionClass name
(preferred term)
BBobject for picking up information and providing a representationsensing object
CCobject for storing for subsequent retrievalstoring object
EEobject for emittingemitting object
FFobject for protecting against the effects of dangerous or undesirable conditionsprotecting object
GGobject for providing a controllable flowgenerating object
HHobject for treating mattermatter processing object
KKobject for treating input signals and providing an appropriate outputinformation processing object
MMobject for providing mechanical movement or forcedriving object
NNobject for enclosing partly or fully another objectcovering object
PPobject for providing perceptible informationpresenting object
QQobject for controlling access or flowcontrolling object
RRobject for restricting or stabilisingrestricting object
SSobject for detecting a human action and providing an appropriate responsehuman interacting object
TTobject for transformingtransforming object
UUobject for structural positioning of other objectsholding object
WWobject for leading from one place to anotherguiding object
XXobject for interfacing an objectinterfacing object

Changes to the standard

RDS/81346 deals with systems and their relations. The output from 81346 is a reference designation which designates systems and their elements. There are three kind of relations to be used: Part-of relations (see 81346-1), Type-of relation (see 81346-2, 2019 edition) and pragmatic relations (to handle non-hierarchal relations for example for interface among systems).

In relation to the update of 81346-2, it became clear that the classification provided needed an update with new definitions following rules from ISO 704 and sub-classes controlled by type-of relations.

The differences between the 2009 and 2019 editions are shown below:

IEC 81346-2: 2009 editionNEW IEC 81346-2: 2019 edition
InterdisciplinaryInterdisciplinary (expanded)
Two-letter classificationThree-letter classification
Implemented in object librariesStability for object libraries
Type-of relations not clearType-of relations 100% perfect
Backwards compability to 1996 editionBackwards compability to 2009 edition
Entry class:
Intended purpose or task (unstable)
Entry class:
Inherent function (stable)
Definitions missing or unclearDefinitions for all classes implemented

With the 2019 edition it is now possible to distinguish between a door and a window, but also between a temperature transmitter and a temperature switch and so on.

Class codeClass definitionClass name
(preferred term)
Qobject for controlling access or flowcontrolling object
QQobject for controlling access or flow to a spacespace access object
QQCobject for controlling access or flow to a space for use by personsdoor

Inclusion of alternative industry terms
The new edition is backwards compatible with the 2009 edition but now with crystal clear definitions of each class. This has also opened the possibility to include a range of different terms from any industry to be assigned to the updated classification in 81346-2, as the examples of terms with GPA shows below.

Class codeClass definitionClass name
(preferred term)
Examples of terms
Gobject for providing a controllable flowgenerating object
GPobject for providing a controllable flow of liquidliquid flow generating object
GPAobject for providing a controllable flow of liquid by forcing trapped liquid to the discharge sidepositive displacement pumpperistaltic pump, piston pump, rotary gear pump, screw pump, vacuum pump