Address Space

The Address Space tab is where you choose which PLC variables to expose through OPC-UA and how each user role is allowed to interact with them. The on-screen description reads: "Select PLC variables to expose via OPC-UA. Variable indices are resolved automatically during project compilation."

The tab has three areas: a Namespace URI field at the top, a split pane with the available variables on the left and the selected variables on the right, and a configuration modal that opens whenever you select or edit a variable.

Namespace URI

The Namespace URI sets the OPC-UA namespace under which all your exposed variables live. The helper text reads: "Unique namespace identifier for your OPC-UA address space."

The same value is shown read-only on the Namespace Configuration section of the General Settings tab. Editing it here updates both views.

Available PLC Variables

The left panel shows every variable in the project as a hierarchical tree. The header reads Available PLC Variables and the subtitle is "Select variables to expose". A Filter variables... input at the top of the panel narrows the tree to nodes whose name matches what you type.

Each node in the tree carries a small badge showing what kind of element it is:

Click the chevron on a Program or container node to expand or collapse it. Click the badge or name of a selectable item to open the Configure OPC-UA Node modal.

When you select a structured item (function block, structure, or array), the editor automatically generates default field definitions for every member, mirroring the structure inside OPC-UA. You can adjust permissions field-by-field after that.

Deselecting a structured item also removes all of its descendants from the address space.

Selected for OPC-UA

The right panel lists the variables that are currently exposed. The header reads Selected for OPC-UA and the count line reads, for example, "3 variables configured". When the list is empty, a placeholder reads: "No variables selected. Select variables from the left panel to expose them via OPC-UA."

Each card shows:

• A small badge. V for variables, S for structures, [] for arrays.
• The Display Name in bold.
• The Node ID below it.
• An Edit button (re-opens the Configure OPC-UA Node modal).
• A Remove button (drops the variable from the address space).
• A details block with the source PLC variable, its type, and a permissions summary in the form V:r O:rw E:rw.

Configure OPC-UA Node Modal

Selecting a variable from the left panel. Or clicking Edit on the right. Opens a modal titled Configure OPC-UA Node (or Edit OPC-UA Node when editing). The modal pre-fills sensible defaults that you can override.

Variable Info

A grey info box at the top shows:

• PLC Variable: <POU>:<variable path> (for example, main:ked).
• Type: the IEC 61131-3 type.

These two values are read-only. They describe the source variable.

Identification

Access Permissions

A grey Access Permissions panel contains three dropdowns, one per role. Each dropdown offers three options:

The defaults for a new node are:

The on-screen helper text reads: "Configure access permissions for each user role."

Array Information

If the source variable is an array, a cyan-coloured Array Information box shows:

• Dimensions: the array bounds, for example [0..9] or [1..3, 1..3].
• Element Type: the IEC type of each element.
• Total Elements: the total number of elements.

This panel is read-only.

Structure Information

If the source variable is a structure or function block, a Structure Information box shows:

• Type: the IEC type name (for example, TON).
• Fields: the number of member fields.

Field Permissions

For structures, function blocks, and arrays, an additional Field Permissions table appears below the parent permissions. Each row is one field with three role-specific permission dropdowns rendered as compact R / W / RW selects.

A button labelled Apply Parent Permissions to All copies the parent's Viewer / Operator / Engineer permissions to every field, including nested fields. Use this when you want all members to share the parent's access policy, then adjust individual rows where needed.

The footer text reads: "Configure individual permissions for each field. Use 'Apply Parent Permissions' to set all fields to match the parent variable."

Validation

The validation messages displayed by the modal include:

• "Node ID is required"
• "Node ID must be 128 characters or less"
• "A node with this ID already exists"
• "Browse name is required"
• "Browse name must be 64 characters or less"
• "Display name is required"
• "Display name must be 128 characters or less"

Saving

The primary button reads Add to Address Space for new nodes and Save Changes when editing. Cancel discards the form.

IEC 61131-3 to OPC-UA Type Mapping

The runtime maps each IEC 61131-3 data type to an OPC-UA built-in type. You do not select the OPC-UA type yourself. It is chosen automatically based on the source variable's IEC type.

Best Practices

• Keep your address space focused: expose only the variables the client actually needs. A smaller address space starts faster and is easier for operators to navigate.
• Use the role permissions to enforce safety. Viewers should never be able to write to setpoints; operators should only write where the process tolerates it; reserve all configuration writes for engineers.
• Choose Node IDs that include the source POU name. The auto-generated PLC.<POU>.<path> form is usually a good fit.
• Store free-form context in the Description field. It shows up in client browsers and helps operators understand what each node does.

What's Next?

• Worked Example: see the address space wired up end-to-end with a worked configuration.
• Users: confirm your role assignments match the permissions you set per variable.
• General Settings: review the cycle time if address-space updates feel too slow or too fast.