Applications should properly support the three characteristics of UIDs to avoid problems retrieving published data.
Three Characteristics of UIDs
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UIDs are unique. There should not be two objects with the same UID.
If the same tool publishes the same object as part of two different document types with potentially two different class definitions, then that object can, and probably should, have the same UID. For example, if instrument A is published as an instance of class CA for one document type and as an instance of class CB for a second document type, then it should be published with the same UID for both document types.
UIDs are intended to uniquely identify the object, not the published instance. The same object published twice (potentially as instances of two class definitions) is the same object and should have the same UID.
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UIDs are persistent. If the same object is published 10 times, it should have the same UID all 10 times.
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UIDs are never reused. If an object is deleted, then its UID should not be assigned to a new object.