Indicates that the source act makes use of (or will make use of) the information content of the target act.

UsageNotes: A usage relationship only makes sense if the target act is authored and occurs independently of the source act. Otherwise a simpler relationship such as COMP would be appropriate.

Rationale: There is a need when defining a clinical trial protocol to indicate that the protocol makes use of other protocol or treatment specifications. This is stronger than the assertion of "references". References may exist without usage, and in a clinical trial protocol is common to assert both: what other specifications does this trial use and what other specifications does it merely reference.