Index: trunk/doc/design/10_forge_imp.html
===================================================================
--- trunk/doc/design/10_forge_imp.html	(revision 8158)
+++ trunk/doc/design/10_forge_imp.html	(revision 8159)
@@ -86,3 +86,15 @@
 project file (e.g. project role configuration) and not on sheet level
 because it affects the abstract model, which uses all sheets of the project.
 
+<p>{imp10:11}
+Now suppose there's an orthogonal property, whether the device is going to
+ha a battery option, which affects whether the board has a battery charger
+circuit. All three models can be shipped with or without the battery option.
+One way to handle this is to double the stance.model values, from 3 to 6,
+so each has a battery and a no-battery variant. But a more elegant solution is
+to keep the original 3 models and use the sub_major stance with two values,
+<i>with-battery</i> or <i>no-battery</i>. The process of creating the stance
+values and creating the DNP forge for the battery charger is the same as above,
+using stance.sub_major instead of stance.model.
+
+