7. A document filing system according to claim 3, wherein said first and second predetermined concepts are superclass concepts, a superclass concept being a concept which represents the highest concept in a related class of concepts, such that all concepts in said class of concepts are subsumed by the superclass concept for said class.
7. A document filing system according to claim 3, wherein said first and second predetermined concepts are superclass concepts, a superclass concept being a concept which represents the highest concept in a related class of concepts, such that all concepts in said class of concepts are subsumed by the superclass concept for said class. 8. A document filing system according to claim 7, wherein said display means displays a generic frame to said user when a new concept is input by said user, said generic frame being generated by said retrieving means based on said instance relations corresponding to all superclass concepts of said new concept.