Propertiesare used to define the characteristics of Nodes. Propertiesare defined using the Variable NodeClass, specified in Table 13. However, they restrict their use.

Propertiesare the leaf of any hierarchy; therefore they shall not be the SourceNodeof any hierarchical References. This includes the HasComponentor HasProperty Reference, that is, Properties do not contain Propertiesand cannot expose their complex structure. However, they may be the SourceNodeof any non-hierarchical References.

The HasTypeDefinition Referencepoints to the VariableTypeof the Property. Since Propertiesare uniquely identified by their BrowseName, all Propertiesshall point to the PropertyType defined in OPC 10000-5.

Propertiesshall always be defined in the context of another Nodeand shall be the TargetNodeof at least one HasProperty Reference. To distinguish them from DataVariables, they shall not be the TargetNodeof any HasComponent Reference. Thus, a HasProperty Referencepointing to a Variable Nodedefines this Nodeas a Property.

The BrowseNameof a Propertyis always unique in the context of a Node. It is not permitted for a Nodeto refer to two Variablesusing HasProperty Referenceshaving the same BrowseName.