Last updated on April 10, 2022
Summary of the most important pieces of information and advice as a quick reference for modelers.
This Post is part of the OPC UA Information Model Tutorial.
Objects, Variables, Properties
source: https://reference.opcfoundation.org/v104/Core/docs/Part3/C.2.2/#TableC.1 (graphical representation is missing in source!)
Variables vs. Properties vs. Attribute
DataVariables can contain other Variables, Properties can not. https://reference.opcfoundation.org/v104/Core/docs/Part3/4.4.1/
Properties (and Attributes) https://reference.opcfoundation.org/v104/Core/docs/Part3/4.4.2/
As another example, function blocks in control systems might be represented as Objects. The parameters of the function block, such as its setpoints, may be represented as DataVariables. The function block Object might also have Properties that describe its execution time and its type.
Properties vs. DataVariables https://reference.opcfoundation.org/v104/Core/docs/Part3/A.4.2/
How to implement structured data
Many Variables and / or structured DataTypes https://reference.opcfoundation.org/v104/Core/docs/Part3/A.4.3/
ObjectType, VariableType and DataType
Every Object, Variable or Data has a base type and any number of instances of these types. It can be seen as Object-Oriented Programming.
You can create your own types by subtyping any existing OPC UA Types
source: https://reference.opcfoundation.org/v104/Core/docs/Part3/C.2.2/#TableC.2 (graphical representation is missing in source!)
The source object has to be a folder or a view. https://reference.opcfoundation.org/v104/Core/docs/Part3/7.11/ _
HasChild, Aggregates and HasComponent ReferenceType
HasChild is an abstract ReferenceType https://reference.opcfoundation.org/v104/Core/docs/Part3/7.5/
Aggregates is an abstract ReferenceType https://reference.opcfoundation.org/v104/Core/docs/Part3/7.6/
Consequently, HasComponent ReferenceType ( https://reference.opcfoundation.org/v104/Core/docs/Part3/7.7/ ) should be most commonly used to hierachically structure nodes.
To create a graphical visualization of your OPC UA Model, the OPC Foundation defines different shapes and arrow types which sould be used.
You can use MS Visio and the provided Template to draw your models.
Note that on some downloadable MS Word specification files, the corresponding visual drawings are embedded Visio files.
The Template is available here as
UA Shapes Visio Template
Alternatively, you can also use Graphviz to create a similar looking visualization.
See: Visualization of OPC UA Information Models using Graphviz
Continue with Step 5