Common Data Model

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As the world of Operational Technology (OT) and Information Technology (IT) converges with the Internet of Things (IoT) and Industrial Internet of Things (IIoT), IT and OT professionals can use the IIoT Core Common Data Model (CDM) to correlate data for troubleshooting and problem solving.

How does the Common Data Model work?

Each asset (sensors, machines, devices) generates a different data type and structure and CDM defines the data schema in which components exchange information with IIoT Core Services.

You can also use CDM to route certain data types (time series, binaries, structured, and unstructured) to specific destinations that you configure based on a tag in the model. A single CDM instance can be routed to one or more destinations, including storage media or network protocols. For example, an instance of the CDM containing AMQP data can be simultaneously routed to a time series database and a remote messaging broker.

The CDM uses language-neutral protocol buffers (protobuf) for arranging structured data in a series. For general information about how to create custom alerts, see Create custom alerts.

If you need a language-specific CDM object definition, contact your HV representative.

The IIoT Core Services CDM has the following parts:

Common Data Model data structure

The CDM contains the following structural elements:

HiotaMessage
Top-level message within the system which includes:
- Unique message identifier
- Message creation time stamp
- Unique identifier of the source
- For HiotaMessages that fail and are routed to an error topic, an error message stating the reason for failure
- Asset information
- Unique identifier of asset
- Asset name
OTData
Contains one or more data sensor readings from the IIoT Gateway device.
It represents a single attachment data point for sending single points of data, such as documents, images, and JSON. For an array, use the generic list.
ITData
Contains IT data of the edge devices:
- Unique asset identifier, such as a UUID, URL, or a friendly name for an asset, such as "Train cabin thermostat".
- Power supply or battery
- CPU
- Memory
- Boot time
- Disks
- Asset location (longitude and latitude)
- Connectivity status:
  - Bluetooth
  - Wi-Fi (network name, security type, Wi-Fi address)
  - Network
  - Cellular and SIM
Alert Data
Contains information about an alert to be ingested and stored:
- Alert name
- Alert description
- Alert severity
- Alert type
- Notifications
  - EmailMessage
    - subject
    - body_content_type
    - body
    - recipients
  - PushNotificationMessage
    - APNsPayload
      - Aps
        AlertString
        Alert
        Title
        SubTitle
        Body
        LocKey
        LocArgs
        TitleLocKey
        TitleLocArgs
        SubTitleLocKey
        SubTitleLocArgs
        ActionLocKey
        LaunchImage
        Badge
        Sound
        Critical Sound
        ContentAvailable
        MutableContent
        Category
        ThreadID
        CustomData

Alert Data object details

You can use the CDM to create a custom alert using the alert_data object described in this section.

A custom alert is created based on the alert_data value that is found in the CDM definition. The alert_data object contains the following fields:

Field	Description
name	Short name of the alert.
description	Description of the alert.
severity	The alert severity accepts one of the following values: ALERT_SEVERITY_UNKNOWN ALERT_SEVERITY_NORMAL ALERT_SEVERITY_WARNING ALERT_SEVERITY_CRITICAL
type	The following alert types are available: ALERT_TYPE_UNKNOWN ALERT_TYPE_CUSTOM ALERT_TYPE_HIGH_CPU ALERT_TYPE_HIGH_MEMORY ALERT_TYPE_LOW_DISK_SPACE ALERT_TYPE_SERVICE_DOWN
notification	Array of notification type. For more information about email notifications, see Set up email notifications.