Claudia Ermel Karsten Ehrig View Transformation in Visual Environments applied to Algebraic High-Level Nets. 61-86 2005 127 Electr. Notes Theor. Comput. Sci. 2 http://dx.doi.org/10.1016/j.entcs.2005.02.006 db/journals/entcs/entcs127.html#ErmelE05