Mannhardt, Ch.Schrack, G.C. E. Vandoni2015-09-292015-09-2919801017-4656https://doi.org/10.2312/eg.19801019The definition, manipulation and display of graphical data in an applications program can occur at different levels if graphical data are viewed as a hierarchy of output primitives. This paper discusses concepts of how graphical objects may be defined and desribes how these concepts are reflected in the design of the high-level graphics programming language LIG/P.10.2312/eg.19801019