intermediate primitive concepts (unless medically necessary and impossible to define with existing concept model). an intermediate primitive (=not defined) concept is a non-defined concept that has children concepts and parent concepts. this convention is related to the use of description logic to facilitate terminology maintenance. because primitive concepts can not be processed by the description logic classifier, the maintenance of such concepts relies solely on human editors. adding new intermediate primitive concepts requires changes to all affected concepts and is demanding in terms of terminology maintenance.