Promise¶

A Promise is a classification that indicates that the element it is attached to describes a real-world digital resource that has not yet been delivered. The element is a commitment (a promise) that the resource will exist, rather than a description of something that is available today.

Promise elements are created when the lineage graph is being designed ahead of the resources it describes. For example, an information supply chain may show a new data set being produced by a process that is still under development. Cataloguing the data set with the Promise classification allows the lineage relationships to be created and reviewed before the resource is built, and lets consumers see what is coming.

The element is not returned to callers unless the caller specifies the forLineage parameter. If it is set to true, the Promise classification is ignored and the element is returned. This prevents a promised resource appearing in catalog searches as if it were ready to use.

The properties of the classification record the delivery plan:

• deploymentStatus and userDefinedDeploymentStatus - how far the delivery has progressed.
• startTime - when work on the resource started.
• dueTime - when the resource is expected to be delivered.
• lastReviewTime - when the delivery progress was last reviewed.
• completionTime - when the resource was delivered.

Once the resource is delivered, the Promise classification is removed and the element becomes visible to all callers. The classification can be attached to any OpenMetadataRoot entity.

Managing promises¶

The Classification Explorer API provides the operations to add and remove the classification:

• setElementAsPromise adds the Promise classification, with its delivery plan properties, to an existing element. From that point the element is only returned to lineage requests.
• clearElementAsPromise removes the classification once the resource has been delivered. The request must set forLineage=true, because the promised element is invisible to the request otherwise.

A promised element still reserves its qualifiedName. A request to create another element with the same unique name fails while the promise is in place, which stops a second catalog entry being created for the resource when it is finally delivered. This is different from a Memento element, whose unique name is released for reuse.

Elements with the Promise classification are shown with their own visual style in Egeria's mermaid graphs, so that planned resources are easy to distinguish from those that are available.

Promise and Memento¶

Promise and Memento mark the two ends of an element's life in a lineage graph:

• A Promise element describes a resource that does not exist yet.
• A Memento element describes a resource that no longer exists.

Both are hidden from normal catalog queries and both are returned when forLineage=true, so that the lineage graph remains complete from the planned origins of the data through to resources that have since been retired.

Raise an issue or comment below