1SUTHERLAND I E.A man-machine graphical communication system[C] //Proceedings of the Spring Joint Computer Conference.Detroit,Mich.,USA:Spartan Book,1963:329-345.
2BORNING A H.The programming language aspect of thing lab[J] .ACM Transaction on Programming Language and System,1984,3(4):353-387.
3HEYDON A,NELSON G.The juno-2 constraint-based drawing editor[R] .Palo Alto,Cal.,USA:Semiconductor Research Center Rsearch Report 131a,1986:341-354.