---
description: Understand how the MES Resource hierarchy becomes the OPC UA Resource base NodeId and functional node tree.
alias: userguide-equipment-integration-opcua-standard-address-space
---

# OPC UA Address Space

## From MES Hierarchy to Resource Base Node

[MES Modeling](mes-modeling.md) defines where the physical equipment sits in the MES hierarchy. This page starts from that approved model and explains how it becomes the OPC UA address-space identity used at runtime.

During controller setup, the integration:

1. Reads `Namespace` from the selected OPC UA Server profile.
2. Builds the string identifier from the Resource's relevant MES hierarchy.
3. Combines both values into a fully qualified string NodeId.
4. Stores the result in the read-only Resource attribute `IndEqOpcUaBaseNodeId`.

Example:

| Input | Value |
| --- | --- |
| MES hierarchy path | `Northwind.PortoPlant.PackagingHall.FillingArea.Line01.Filler01` |
| Selected profile's `Namespace` | `2` |
| Generated `IndEqOpcUaBaseNodeId` | `ns=2;s=Northwind.PortoPlant.PackagingHall.FillingArea.Line01.Filler01` |

The optional SubArea or Production Line segment appears only when it is part of the MES model. This page does not define the equipment placement; it describes the resulting OPC UA identity.

## Functional Structure

Below the base node, the **Common Data Model** based structure organizes the interface into four functional folders. The handshake nodes inside those folders are part of this Industrial Equipment implementation.

```mermaid
flowchart LR
    BASE("Resource Base <br/>NodeId")

    BASE --> OP("Operation")
    BASE --> RECIPE("Recipe")
    BASE --> DATA("Data Collection")
    BASE --> STATE("State")

    OP --> TI("Track In")
    OP --> TO("Track Out")
    OP --> AB("Abort")

    RECIPE --> RP("Actual Recipe<br/>Parameters")
    DATA --> DP("Handshake and Actual<br/>Process Parameters")
    STATE --> SP("Main State<br/>Substate<br/>Reason")

    classDef standard fill:#FFFFFF,stroke:#64748B,color:#334155,stroke-width:1.5px;
    classDef secondary fill:#FFFFFF,stroke:#CBD5E1,color:#64748B,stroke-width:1.5px;
    classDef highlight fill:#075C00,stroke:#075C00,color:#FFFFFF,stroke-width:1.5px;

    class BASE highlight;
    class OP,RECIPE,DATA,STATE standard;
    class TI,TO,AB,RP,DP,SP secondary;

    linkStyle default stroke:#94A3B8,stroke-width:1.5px;
```

## Complete Logical Tree

```text
<BaseNodeId>
├── Operation
│   ├── TrackIn
│   │   ├── Material
│   │   │   └── Name
│   │   ├── MachineOperationRequest
│   │   ├── MESOperationPerformed
│   │   └── MachineOperationConfirmed
│   ├── TrackOut
│   │   ├── Material
│   │   │   └── Name
│   │   ├── MachineOperationRequest
│   │   ├── MESOperationPerformed
│   │   └── MachineOperationConfirmed
│   └── Abort
│       ├── Material
│       │   └── Name
│       ├── MachineOperationRequest
│       ├── MESOperationPerformed
│       └── MachineOperationConfirmed
├── Recipe
│   ├── <ParameterName>
│   └── <ResourceRecipeName>
│       └── <ParameterName>
├── DataCollection
│   ├── Material
│   │   └── Name
│   ├── MachinePostDataRequest
│   ├── MESPostDataPerformed
│   ├── PostDataReadingNumber
│   ├── PostDataSampleId
│   └── Parameters
│       └── <ParameterName>
└── State
    ├── MainState
    ├── SubState
    └── Reason
```

!!! important "Dynamic parameter names"
    Names such as `Recipe.<ParameterName>` and `DataCollection.Parameters.<ParameterName>`, when used in examples, are placeholders. A machine exposes its real parameters, such as `TargetSpeed`, `TorqueTarget`, `ActualCycleTime`, or `InspectionResult`. The OPC UA Tag Names must match the corresponding MES Parameter name. Sub-recipe folder names must match the MES sub-recipe display names.

## Relative Node Construction

`IndEqOpcUaBaseNodeId` already contains the namespace and the string identifier:

```text
ns=<Namespace>;s=<HierarchyPath>
```

The final NodeId for a standard node is created by appending its relative path:

```text
<IndEqOpcUaBaseNodeId>.<RelativeNodePath>
```

Example:

```text
ns=2;s=Northwind.PortoPlant.PackagingHall.FillingArea.Line01.Filler01.Operation.TrackIn.MachineOperationRequest
```

`Namespace` is configured in the selected OPC UA Server profile and is used when `IndEqOpcUaBaseNodeId` is generated. Because namespace indexes can differ between server deployments, verify the selected profile and regenerate or validate the Resource attribute in every environment. See [Configure the OPC UA Connection](../configuration/opcua-connection.md).

## Machine Interface Rules

- Keep the fixed folder and control-node names exactly as documented.
- Use OPC UA `Boolean` values for handshake bits.
- Initialize handshake bits to `false`.
- Give **Connect IoT OPC UA Client** read access to machine-owned nodes and write access to MES-owned nodes.
- Use actual recipe and data collection parameter names.