Update how-to-identity-based-service-authentication.md

Author: deeikele

articles/machine-learning/how-to-identity-based-service-authentication.md

@@ -39,10 +39,12 @@ Azure Machine Learning is composed of multiple Azure services. There are multipl
 
 The Azure Machine Learning workspace uses a __managed identity__ to communicate with other services. Multiple identity types are supported for Azure Machine Learning.
 
-| Managed identity type | Role assignment creation | Description |
+| Managed identity type | Role assignment creation | Purpose |
 | ---- | :----: | :----: |
-| System-assigned | Managed by Microsoft | Lifecycle tied to resource; single resource use; simple to get started |
-| System-assigned+user-assigned | Managed by you | Independent lifecycle for user-assigned identity, multi-resource use, controls least privileged access. |
+| System-assigned (SAI) | Managed by Microsoft | Lifecycle tied to resource; single resource use; simple to get started |
+| System-assigned+user-assigned (SAI+UAI) | Managed by you | Independent lifecycle for user-assigned identity, multi-resource use, controls least privileged access. Access data in training jobs. |
+
+Once a workspace is created with SAI identity type, it can be updated to SAI+UAI, but not back from SAI+UAI to SAI. You may assign multiple user-assigned identities to the same workspace. 
 
 To learn more about managed identity in Azure, see [Manage user-assigned managed identities](../entra/identity/managed-identities-azure-resources/how-manage-user-assigned-managed-identities).
 
@@ -178,7 +180,6 @@ Not supported currently.
 > [!TIP]
 > To add a new UAI, you can specify the new UAI ID under the section user_assigned_identities in addition to the existing UAIs, it's required to pass all the existing UAI IDs.<br>
 To delete one or more existing UAIs, you can put the UAI IDs which needs to be preserved under the section user_assigned_identities, the rest UAI IDs would be deleted.<br>
-To update identity type from SAI to UAI|SAI, you can change type from "user_assigned" to "system_assigned, user_assigned".
 
 ### Compute cluster