ISO/IEC 81346-2 Series
The 81346-2:2019
The 81346-2 series establishes classification schemes with defined object classes and their associated letter codes and is primarily intended for use in reference designations of generic components.
The recent edition of the 81346-2 series is the result of extensive work both by ISO and IEC updating the standard to make it applicable in a broader set of industries and to provide users with the option to apply more detailed classification when creating reference designations.
The reason for updating the 2009 edition to the current one was to comply with the rules of type-of relations, and the 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 stable classification throughout the entire object life cycle.
The third letter code
One of the major changes in the 81346-2:2019 was the introduction of the third letter code. A third letter was introduced in the component system classification to improve the navigation and recognition of a system and functions as a sub-classification for the TWO letter code(s).
GQA is a sub-type of GQ, and GQ is a sub-type of G
Moreover, in relation to the update, it became clear that the classification needed an update with new definitions following rules from ISO 704 and sub-classes solely controlled by type-of relations.
The Fundamentals
The Letter Codes
A common technical language realized by letter codes is necessary for most reference designation systems that are cross-disciplinary. The letter codes provide essential information as it gives you instant recognition of what kind of system it is.
The letter codes establish the common ground for interdisciplinary understanding of systems. Naming conventions for meaningful abbreviations are not reliable enough to convey information among different parties, in different industries, and with different mindsets. There is a need for common letter codes that everyone understands.
So, when the terminology grows, the trick is to classify it. To classify means to create a description of a set of objects that share one or more properties. This is what the ISO/IEC 81346 standard series has done for systems and system elements.
There is a total of 17 generic entry classes (Main systems) in 81346-2.
The letter codes are interdisciplinary and cover everything inside the scope of the standard.
The Classification
When classifying a system and its elements, you can use up to three letter codes as a part of the reference designation. It is most effective to use all three letter codes on different abstraction levels, as follows:
ONE letter code for designation of high-level (main) systems
TWO letter code for designation of mid-level (technical) systems
THREE letter code for designation of low-level (component) systems
Even though there are three levels of abstraction, i.e., One-Two-Three letter codes to choose from, this does not mean you always have to use all of them and in the 1-2-3 sequence.
It works more like Lego bricks. The 81346 standard has sorted terms for you, and you can build any reference designation you like.
Industry Specific Classifications
When modeling systems in certain industries, specific and more accurate class libraries would be preferable. It turned out that the generic classifications given by 81346-2 were, in some industries, too abstract and generic to fit into specific industry domains.
As a result, the standard and its principles naturally evolved over the years with the development of industry-specific classifications. The current series is available, and the upcoming series is already in development.