Node Management¶

Demonstrates how to extend the server's address space at runtime from the client side, using the high-level o6.Client API. The example adds an Object, a Variable, a Method, and an ObjectType, links two Objects with an explicit reference, browses the result, and finally deletes everything it created.

The example talks to S03_firststeps.py.

This example needs a running server

Start Server First Steps first:

python examples/server/S03_firststeps.py

The relevant API surface lives on the o6.Client instance:

addObjectNode / addVariableNode / addMethodNode / addObjectTypeNode
addReference / deleteReference
deleteNode (accepts a single NodeId or a list)

All add*Node calls are keyword-only and return the NodeId the client (or the server, if none was requested) chose for the new node.

1. Connection Setup¶

The endpoint URL is the same one S03_firststeps.py listens on. The Objects folder (i=85) is the conventional parent for user-defined nodes, and Organizes (i=35) is the standard "folder contains folder" reference type used to attach a new node to its parent.

localhost = "localhost"
endpoint_url = EXAMPLE_ENDPOINT

OBJECTS_FOLDER = "i=85"
ORGANIZES = "i=35"

print("--- 1. Connection Setup ---")
print(f"Connecting to {endpoint_url} ...")

2. Add an Object Node¶

Every node creation follows the same shape: build an *Attributes struct, set the human-readable fields (displayName, description), and pass the struct to the matching add*Node method along with parent, browseName, and the reference type that connects the new node to its parent.

browseName can be either a plain string or an o6.QualifiedName; passing o6.QualifiedName(1, "MyFolder") explicitly places the new node in namespace 1, the same namespace S03_firststeps.py uses for its own objects.

Every add*Node call also accepts a requestedNodeId= keyword (e.g. requestedNodeId="ns=1;i=5000") to pin a stable address for the new node; omitting it lets the server pick one. The server-side equivalent is the nodeId= keyword on addObject / addVariable / addMethod.

with Client(endpoint_url) as client:
    print("Connected.")

    print()
    print("--- 2. Add an Object Node ---")
    obj_attr = ObjectAttributes()
    obj_attr.displayName = o6.LocalizedText("MyFolder")
    obj_attr.description = o6.LocalizedText("An example folder object")

    folder_id = client.addObjectNode(
        parent=OBJECTS_FOLDER,
        browseName=o6.QualifiedName(1, "MyFolder"),
        attributes=obj_attr,
        parentReference=ORGANIZES,
    )
    print(f"Added object: {folder_id}")

3. Add a Variable Node¶

VariableAttributes is the only one of the four attribute types that carries a value: the initial value of the variable. valueRank = -1 means scalar; positive values indicate an array of that rank. accessLevel = 3 means "readable and writable".

print()
print("--- 3. Add a Variable Node ---")
var_attr = VariableAttributes()
var_attr.displayName = o6.LocalizedText("Temperature")
var_attr.description = o6.LocalizedText("A temperature sensor value")
var_attr.value = o6.Double(21.5)
var_attr.dataType = o6.NodeId(11)  # i=11 in ns=0 is the Double data type
var_attr.valueRank = -1  # scalar
var_attr.accessLevel = 3  # readable + writable
var_attr.userAccessLevel = 3

temp_id = client.addVariableNode(
    parent=folder_id,
    browseName=o6.QualifiedName(1, "Temperature"),
    requestedNodeId="ns=1;i=5001",  # pin a stable address
    attributes=var_attr,
)
print(f"Added variable: {temp_id}")

# Read back the initial value we just stored on the server
initial = client.read(temp_id)
print(f"Initial value = {initial}")

4. Add a Method Node¶

Adding a method node is structurally identical to adding an object: build a MethodAttributes and call addMethodNode. The node exists once this call returns, but it is not invokable until the server registers a callback for it — S03_firststeps.py does not register one for Reset, so a later client.call(method_id, ...) would return BAD_NOT_IMPLEMENTED.

print()
print("--- 4. Add a Method Node ---")
method_attr = MethodAttributes()
method_attr.displayName = o6.LocalizedText("Reset")
method_attr.description = o6.LocalizedText("Reset the sensor")
method_attr.executable = True
method_attr.userExecutable = True

method_id = client.addMethodNode(
    parent=folder_id,
    browseName=o6.QualifiedName(1, "Reset"),
    attributes=method_attr,
)
print(f"Added method: {method_id}")

5. Add an ObjectType Node¶

ObjectTypes are templates, so adding one to the address space does not affect existing objects. To use it, add an object node whose typeDefinition references the new ObjectType's NodeId.

print()
print("--- 5. Add an ObjectType Node ---")
objtype_attr = ObjectTypeAttributes()
objtype_attr.displayName = o6.LocalizedText("SensorType")
objtype_attr.description = o6.LocalizedText("A custom sensor type")
objtype_attr.isAbstract = False

objtype_id = client.addObjectTypeNode(
    parent="i=58",  # BaseObjectType
    browseName=o6.QualifiedName(1, "SensorType"),
    attributes=objtype_attr,
)
print(f"Added ObjectType: {objtype_id}")

6. Browse the New Object's Children¶

client.browse(nodeid) returns the list of references leading out from the given node. With result_mask=BrowseResultMask.ALL each reference carries every field (browse name, display name, node class, type definition, ...).

print()
print("--- 6. Browse the New Object's Children ---")
print("MyFolder children:")
for ref in client.browse(folder_id, resultMask=ns0dt.BrowseResultMask.ALL):
    print(
        f"  {ref.browseName}  class={ref.nodeClass}  "
        f"forward={ref.isForward}  target={ref.nodeId}"
    )

7. Add an Explicit Reference Between Two Objects¶

To demonstrate addReference / deleteReference we add a second folder and create an Organizes reference from MyFolder to MyFolder2 — a forward reference to a sibling, the simplest valid case.

print()
print("--- 7. Add an Explicit Reference Between Two Objects ---")
obj_attr2 = ObjectAttributes()
obj_attr2.displayName = o6.LocalizedText("MyFolder2")
obj_attr2.description = o6.LocalizedText("A second folder object")

folder2_id = client.addObjectNode(
    parent=OBJECTS_FOLDER,
    browseName=o6.QualifiedName(1, "MyFolder2"),
    attributes=obj_attr2,
    parentReference=ORGANIZES,
)
print(f"Added second object: {folder2_id}")

add_status = client.addReference(
    source=folder_id,
    reftype=ORGANIZES,
    target=folder2_id,
)
print(f"Added reference {folder_id} -Organizes-> {folder2_id}, status = {add_status}")

print("MyFolder children after adding the reference:")
for ref in client.browse(folder_id, resultMask=ns0dt.BrowseResultMask.ALL):
    print(
        f"  {ref.browseName}  class={ref.nodeClass}  "
        f"forward={ref.isForward}  target={ref.nodeId}"
    )

del_status = client.deleteReference(
    source=folder_id,
    reftype=ORGANIZES,
    target=folder2_id,
)
print(f"Deleted reference {folder_id} -Organizes-> {folder2_id}, status = {del_status}")

print("MyFolder children after deleting the reference:")
for ref in client.browse(folder_id, resultMask=ns0dt.BrowseResultMask.ALL):
    print(
        f"  {ref.browseName}  class={ref.nodeClass}  "
        f"forward={ref.isForward}  target={ref.nodeId}"
    )

8. Clean Up¶

deleteNode accepts either a single NodeId or a list of NodeIds. deleteTargetReferences defaults to True, so the Organizes reference created above is removed as part of the second folder's deletion.

    print()
    print("--- 8. Clean Up ---")
    targets = [method_id, temp_id, objtype_id, folder2_id, folder_id]
    del_statuses = client.deleteNode(targets)
    for target, status in zip(targets, del_statuses):
        print(f"Delete {target}: {status}")
        status.check()

print()
print("=== Example completed ===")

Source Code¶

Download C07_nodemanagement.py to run it locally.