In 8.2.9the standard Objectis introduced as entry point for DataTypesthat the Serverwishes to expose in the AddressSpace. When using DataTypeSystemsand DataTypeDictionariesthose Nodes can be referenced by this Objectas well. The standard Objectuses Organizes Referencesto reference Objectsof the DataTypeSystemTyperepresenting DataTypeSystems. Referenced by those Objectsare DataTypeDictionariesthat refer to their DataTypeDescriptions. However, it is not required to provide the DataTypeSystem Objects, and the DataTypeDictionaryneed not to be provided.

Because DataTypesare not related to DataTypeDescriptionsusing hierarchical References, DataType Nodesshould be made available using Organizes Referencespointing either directly from the “DataTypes” Objectto the DataType Nodesor using additional Folder Objectsfor grouping purposes. The intent is that all DataTypesof the Serverexposed in the AddressSpaceare accessible following hierarchical Referencesstarting from the “DataTypes” Object. However, this is not required.

Figure D.3 illustrates this hierarchy using the “OPC Binary” and “XML Schema” standard DataTypeSystemsas examples. Other DataTypeSystemsmay be defined under this Object.


Figure D.3– DataTypes Organization

Each DataTypeSystem Objectis related to its DataTypeDictionary Nodesusing HasComponent References. Each DataTypeDictionary Nodeis related to its DataTypeDescription Nodesusing HasComponent References. These Referencesindicate that the DataTypeDescriptionsare defined in the dictionary.

In the example, the “DataTypes” Objectreferences the DataType“Int32” using an Organizes Reference. The DataTypeuses the non-hierarchical HasEncoding Referenceto point to its default encoding, which references a DataTypeDescriptionusing the non-hierarchical HasDescription Reference.

In case DataTypeSystemsare used, the standard Objects“OPC Binary” and “XML Schema” defined in D.5.5and D.5.6are connected via a Organizes Referencefrom the “DataTypes” Object.