To get QSIM to work with dot, you need to modify a couple of lines in the file
qr/nq/source/interface/qsim-dot.lispDot generates a postscript file and then ghostview is called to display the postscript file. To use dot you need to change the definition of the following two variables within this file:
+DOT-COMMAND+Currently, both of these command specify a full path. If you have ghostview and dot in your path, then you can simply change them to the function name.
Also, if you are using a listp other than Allegro CL or Lucid CL, then you might need to change the line that makes the system call just as you had to do for POS. Look in the file with the dot code and search for user::shell to find where to do this. It might work right now for kcl and lispworks as well.
Once you have done this, the rest should work fine. For information about displaying the QDE using dot, please see the qsim-extensions.ps manual under the Additional Display Capabilities section.