7.1.6 UA Reference

Equivalent WoT TD definition Additional semantic annotations at property and action level
Description

A reference in OPC UA is used to define the relationship between two nodes. OPC UA defines several hierarchical and non-hierarchical references. In this specification version, a minimal set of references (e.g., HasComponent, HasTypeDefinition) can be used in a TD to represent the relationship between interaction affordances or between a Thing and its interaction affordances.

Some references are defined by own terms (e.g., uav:componentOf") or can be part of @types definitions.

Details about the reference types that are mapped within a TD are provided in Section 7.3.

Snippet example in OPC UA (e.g., as nodeset)


<UAVariable DataType="Double" NodeId="ns=3;i=6125" BrowseName="3:ActualPosition">

<References>

<Reference ReferenceType="HasComponent" IsForward="false">ns=3;i=5001</Reference>
</Reference>

</UAVariable>

Transformed usage in a TD definition (as snippet)

"properties": {

"3:ActualPosition": {
"title": "Actual Position",
"uav:componentOf": ["ns=3;i=5001"],