Graphical Element Design of Universal Symbol Library

Graphical element is basic unit of symbol library,which is designed by indirect information method.Firstly the paper defines the tree structure of symbol library.Secondly,it makes a graphical element's devise based on object-oriented technology.Finally,it expounds mathematic model and implement methods of Hermite curve graphical element and free curve graphical element.The symbol software based on the above is to fulfil the demand for symbolization of computer aided protraction.