HasProperty
In OPC UA, HasProperty is the hierarchical ReferenceType linking a node to a Property: a Variable of type PropertyType holding metadata about its parent. It is identifier i=46 in namespace 0, a subtype of Aggregates, with the inverse name PropertyOf. Properties are leaves and are usually static.
Property versus DataVariable
A Property describes; a DataVariable measures. EURange, EngineeringUnits, InputArguments, EnumStrings and a nameplate SerialNumber are Properties. A temperature, a counter and a machine state are DataVariables, reached by HasComponent. The reference type and the PropertyType type definition are what distinguish them - the NodeClass is Variable in both cases.
Properties must be leaves
Part 3 requires that a Property has no DataVariable children of its own. If you find yourself wanting a nested Property, you actually want a child Object or a Structure DataType. Tools and code generators rely on this rule, so a server that violates it produces models that UaModeler, the ModelCompiler and generic clients handle inconsistently.
The Properties worth reading first
On any analogue node, EURange and EngineeringUnits turn a bare number into 42.5 degrees C with a range of 0 to 100. On a Method, InputArguments and OutputArguments give you the full signature. On a discrete node, EnumStrings or EnumValues give the state texts. Reading these once at startup and caching them is standard practice, since they rarely change and subscribing to them at process rates wastes queue space.
Example
Properties on an AnalogItemType Variable
Mixer_01
--HasComponent--> Temperature Variable, AnalogItemType, Double
--HasProperty--> EURange Range { Low 0, High 100 }
--HasProperty--> EngineeringUnits EUInformation
NamespaceUri http://www.opcfoundation.org/UA/units/un/cefact
UnitId (UNECE Rec 20 code)
DisplayName "degC"
Description "degree Celsius"
--HasProperty--> InstrumentRange Range { Low -20, High 150 }
Rendered by a client that reads them: 42.5 degC [0 .. 100]
Rendered by one that does not: 42.5Defined in: Part 3 - Address Space Model, standard ReferenceTypes and the Property definition; Part 8 - Data Access for EURange and EngineeringUnits.
Last verified 7 September 2026 against OPC UA 1.05.07. OPC UA Connect is an educational resource and is not affiliated with the OPC Foundation.