About 81346-2 (New 2018 edition!)

“Stabilize the codes – but please do not make any changes!” was the task given to the maintenance team in 2014, when we decided to introduce the third letter code in 81346-2. We have worked hard to make the update, which is now in its Final draft ready for voting by the national standardization committees. We expect the new edition to be published by the end of 2018. The standard is currently available in the Committee Draft version.

The background for the update: We saw the benefit of applying RDS in the construction industry, but had the problem that “QQ” was used for both doors and windows in the existing edition. So we had to introduce a third letter code to make sure that a door is a door! With the third letter code, class QQA now holds a window, and class QQC holds a door and all related terms for doors.

Furthermore, we also recognised the need to make the codes 100% life cycle stable, so a code would not need to change when first assigned. We also missed a mechanism to allow all different kind of terms to be allocated to a letter code, without changing the meaning of the class. We therefore had to make clear and precise definitions of each class too, now based on the rules given in ISO 704.
The new proposal is a CD (Committee Draft), now out in international hearing, but we think the result is very useful, and therefore would like to introduce it to you in brief here.

Entry classes

There are 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 manual action and providing an appropriate responsemanual 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 is about 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, 2018 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 2018 editions are shown below:

IEC 81346-2: 2009 editionNEW IEC 81346-2: 2016 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

So you can now 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