What concept is applied when a classification is derived directly from an existing classified document?

The correct concept applied when a classification is derived directly from an existing classified document is "Derived From." This term indicates that the new classified information is based on or originates from the content of an existing classified document. The classification of the new information must reflect the classification level of the source document from which it is derived, ensuring that sensitive information remains protected in a consistent manner.

Using "Contained In" would not accurately convey this relationship between the new and existing classifications. "Contained In" suggests that the new information is simply found within the existing document but does not emphasize the derivation of classification. "Explicit Classification" refers to a clearly defined classification level applied directly to information rather than indicating its source. "Aggregation" involves combining multiple pieces of information to create a new classification, which is not the case when deriving from a single existing document.