Table 2.

Knowledge representation: main types of concepts

Concept type	Description	Examples
Structure	organization of entries; no meaning for information extraction	measurements, assessment
Object	anchor for ambiguous attributes; definition of a complex frame	aortic valve, mitral valve
Object attribute	type of information with ambiguous meaning; it requires an object context	regurgitation (aortic)
Attribute	unambiguous type of information stated in reports	LVEF, E/E’
Value	specific state of an attribute	present, absent, severe