title: fragment/common
description: Common schema fields for event schemas
$id: /fragment/common/2.0.0
$schema: https://json-schema.org/draft-07/schema#
type: object
additionalProperties: false
properties:

  $schema:
    type: string
    description: >
      A URI identifying the JSONSchema for this event. This should
      match an schema's $id in a schema repository.
      E.g. /schema/title/1.0.0

  ### Meta data object.  All events schemas should have this.
  meta:
    type: object
    properties:
      uri:
        type: string
        format: uri-reference
        maxLength: 8192
        description: Unique URI identifying the event or entity
      request_id:
        type: string
        description: Unique ID of the request that caused the event
      id:
        type: string
        description: Unique ID of this event
      dt:
        type: string
        format: date-time
        maxLength: 128
        description: Time the event was received by the system, in UTC ISO-8601 format
      domain:
        type: string
        description: Domain the event or entity pertains to
        minLength: 1
      stream:
        type: string
        description: Name of the stream (dataset) that this event belongs in
        minLength: 1
    required:
      - stream
  dt:
    type: string
    format: date-time
    maxLength: 128
    description: >
      ISO-8601 formatted timestamp of when the event occurred/was generated
      in UTC), AKA 'event time'. This is different than meta.dt, which
      is used as the time the system received this event.

required:
  - $schema
  - meta
  - dt