Medical knowledge representation for medical report analysis

We present a knowledge representation formalism designed for medical knowledge-based applications, and more particularly for the analysis of descriptive medical reports. Knowledge is represented at two levels: a definitional level which describes general medical concepts and the relations between them, and an assertional level, where individual cases are represented. At the definitional level, a concept type hierarchy and a set of schematic graphs define the concepts used and the relations between them, as well as different types of cardinality restrictions on these relations. A compositional hierarchy with a set inclusion relation allows concept composition to be precisely defined. At the assertional level, graphs representing ''instances'' of this knowledge can be created and manipulated taking into account the knowledge defined at the definitional level.