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Dataref (Claim Check Pattern)

As defined by the term Data, CloudEvents MAY include domain-specific information about the occurrence. When present, this information will be encapsulated within the data attribute. The dataref attribute MAY be used to reference another location where this information is stored. The information, whether accessed via data or dataref MUST be identical.

Both the data and dataref attribute MAY exist at the same time. A middleware MAY drop the data attribute when the dataref attribute exists, it MAY add the dataref attribute and drop the data attribute, or it MAY add the data attribute by using the dataref attribute.

Attributes

dataref

  • Type: URI-reference

  • Description: A reference to a location where the event payload is stored. The location MAY not be accessible without further information (e.g. a pre-shared secret).

    Known as the "Claim Check Pattern", this attribute MAY be used for a variety of purposes, including:

    • If the Data is too large to be included in the message, the data attribute is not present, and the consumer can retrieve it using this attribute.
    • If the consumer wants to verify that the Data has not been tampered with, it can retrieve it from a trusted source using this attribute.
    • If the Data MUST only be viewed by trusted consumers (e.g. personally identifiable information), only a trusted consumer can retrieve it using this attribute and a pre-shared secret.

    If this attribute is used, the information SHOULD be accessible long enough for all consumers to retrieve it, but MAY not be stored for an extended period of time.

  • Constraints:

    • OPTIONAL

Examples

The following example shows a CloudEvent in which the event producer has included both data and dataref (serialized as JSON):

{
    "specversion" : "0.3",
    "type" : "com.github.pull.create",
    "source" : "https://github.com/cloudevents/spec/pull/123",
    "id" : "A234-1234-1234",
    "datacontenttype" : "text/xml",
    "data" : "<much wow=\"xml\"/>",
    "dataref" : "https://github.com/cloudevents/spec/pull/123/events/A234-1234-1234.xml"
}

The following example shows a CloudEvent in which a middleware has replaced the data with a dataref (serialized as JSON):

{
    "specversion" : "0.3",
    "type" : "com.github.pull.create",
    "source" : "https://github.com/cloudevents/spec/pull/123",
    "id" : "A234-1234-1234",
    "datacontenttype" : "text/xml",
    "dataref" : "https://tenant123.middleware.com/events/data/A234-1234-1234.xml"
}