For the classification of assets, this specification uses dictionary references, as defined in OPC 10000-19. Dictionary references allow to reference external dictionaries like IEC Common Data Dictionary or ECLASS. This can be used to classify the assets according to those external dictionaries. In Figure 9, an example is given. There are two different classification schemas: “SomeClassification” and “OtherClassification”, the first one using IRDIs and the second URIs. In the example, two of the assets, Asset1 and Asset2, use both classification schemas, one classifying as flow transmitter, and the other as field device. The third asset, Asset3, only uses the second classification schema and classifies as machine. The concept of dictionary references allows to expose many classification schemes, all managed under the standardized Dictionaries Object of the Server Object.
This specification does not further define what external dictionaries should be used for classification. Companion specifications may suggest or mandate specific external dictionaries for specific types of assets.