Update file README.md

demos/demo2/README.md

+### General
+
 The latest version of the demo consists mainly of three communication partners: demo2_dzwald.py, demo2_forestmanager.py (which represents the Dienstleister) and demo2_forestmanager_waldbesitzer.py (which as the name implies represents the forest owner).
 
 demo2_dzwald.py uses the S3IBServer Component from broker_api.py to expose an underlying AAS through the AAS-Interface. 
@@ -95,6 +97,46 @@ event: model.BasicEventElement = await client.getValue(dzwald_id, dzwald_endpoin
                                                         /submodel/submodelElements/Auftragsstatus_Updated")
 auftragsstatus_updated = await client.awaitEvent(event.message_topic)
 ```
+### Operations
+
+Operation Submodelelements can be thought of operation descriptions. The actual callable/invokable is added to the S3IBServer (alongside the operation path for authorization purposes):
+
+```
+getHolzpreisbereich_op = model.Operation(
+        id_short="getHolzpreisbereich", 
+        input_variable=[model.OperationVariable(model.Property(
+            id_short="HolzlisteId",
+            value_type=model.datatypes.String
+        ))]
+    )
+holzliste.add_referable(getHolzpreisbereich_op)
+
+...
+
+def getHolzpreisbereich(provider: api.ModelProvider, HolzlisteId: str):
+    ...
+    return reply
+
+...
+
+callable = lambda **kwargs : getHolzpreisbereich(provider, **kwargs)
+operation_path = f"/aas/submodels/{helpers.encode_id(HolzlisteId)}/submodel/submodelElements/getHolzpreisbereich"
+server.add_callable(operation_path, callable)
+
+```
+
+Invoke the Operation using S3IBAsyncClient's invokeOperation method:
+
+```
+HolzlisteId = "https://www.company.com/holzliste/1"
+reply4 = await client.invokeOperation(
+    dzwald_id,
+    dzwald_endpoint,
+    f"/aas/submodels/{helpers.encode_id(HolzlisteId)}/submodel/submodelElements/getHolzpreisbereich",
+    {"HolzlisteId": HolzlisteId}
+)
+print(f"result of operation 'getHolzpreisbereich': {reply4}")
+```