1、symbol and layout view use same cdf and callback
2、symbol view related mannual very hard to find, I wonder how to develop a symbol view
3、what the relationship between schemaitc view and specter，cdl，Hspice related view, and how to develop specter，cdl，Hspice related view?
4、schematic view used to draw schematic, when to use specter，cdl，Hspice related view?