7. The system for creating new concepts in existing ontologies according to claim 6 , wherein the new concept expression generator comprises: a shortest path generator for, if the description parts in a new concept description are Part 1 . . . , Part n (N>=1), the headword in each description part are H 1 , . . . , H n , the concepts and properties in each description part Part i are C i1 , . . . , C im and Pro i1 , . . . , Pro iw , where n>=1, m>=0, and w>=0, and m>=0 means no other concept, and w=0 means no property in a corresponding part, then for each C ij where 1<=j<=m, finding the shortest path Path ij from H i to C ij , wherein the path should satisfy the following requirements: a) if w>0, it contains some Pro it where 1<=t<=w, b) it contains no cycle, c) for any node N i in the path, if N i is a class, it is followed by edge E j ; if E j is a property, the destination must be a class or an instance; and if E j is a superClassOf relation, the destination must be a class; a language expression generator for generating a corresponding expression E ij in the certain language by using Path ij generated by the shortest path generator; and a combined expression generator for combining all expressions E ij in each Part i generated in the language expression generator with corresponding relationships to one combined expression CE i based on relations of AND/OR/NOT among C ij , where j is from 1 to m.
7. The system for creating new concepts in existing ontologies according to claim 6 , wherein the new concept expression generator comprises: a shortest path generator for, if the description parts in a new concept description are Part 1 . . . , Part n (N>=1), the headword in each description part are H 1 , . . . , H n , the concepts and properties in each description part Part i are C i1 , . . . , C im and Pro i1 , . . . , Pro iw , where n>=1, m>=0, and w>=0, and m>=0 means no other concept, and w=0 means no property in a corresponding part, then for each C ij where 1<=j<=m, finding the shortest path Path ij from H i to C ij , wherein the path should satisfy the following requirements: a) if w>0, it contains some Pro it where 1<=t<=w, b) it contains no cycle, c) for any node N i in the path, if N i is a class, it is followed by edge E j ; if E j is a property, the destination must be a class or an instance; and if E j is a superClassOf relation, the destination must be a class; a language expression generator for generating a corresponding expression E ij in the certain language by using Path ij generated by the shortest path generator; and a combined expression generator for combining all expressions E ij in each Part i generated in the language expression generator with corresponding relationships to one combined expression CE i based on relations of AND/OR/NOT among C ij , where j is from 1 to m. 8. The system for creating new concepts in existing ontologies according to claim 7 , wherein the certain language is OWL (web ontology language).