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0017 External Identifiers

External identifiers are used to correlate the identifiers used in third party metadata catalogs with open metadata elements.



The ExternalId entity describes an external identifier from a specific third party metadata repository. It includes:

  • The identifier value itself in identifier.
  • The pattern used for the identifier (how it is generated and managed) is stored in keyPattern. These are the values it can take, with the default (and most used) being LOCAL_KEY:

    Value Meaning
    LOCAL_KEY Unique key allocated and used within the scope of a single system.
    RECYCLED_KEY Key allocated and used within the scope of a single system that is periodically reused for different records.
    NATURAL_KEY Key derived from an attribute of the entity, such as email address, passport number.
    MIRROR_KEY Key value copied from another system.
    AGGREGATE_KEY Key formed by combining keys from multiple systems.
    CALLERS_KEY Key from another system can bey used if system name provided.
    STABLE_KEY Key value will remain active even if records are merged.
    OTHER Another key pattern.

The mapping of identifiers can be many-to-many, which is why you see that the ExternalIdLink relationship between the OpenMetadataRoot (open metadata resources) and the ExternalId is also many-to-many.

This relationship includes properties to help to map the OpenMetadataRoot to the external identifier.


There is no guarantee that external identifiers from a third party metadata catalog are globally unique and so the ExternalIdScope relationship links the external identifier to the Referenceable that represents the third party metadata catalog. Typically, this is a type of SoftwareCapability, for example, AssetManager.

Further information

There is an article on managing external identifiers to correlate metadata elements from different types of technologies.

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