Rulers and object annotations

[paul hermeneutic gmail com]

These are basic questions.  I searched the Dia help and the web and
could not find anything.

I would like to display the rulers around the diagram surface borders
in inches.  I set File > Preferences > User Interface tab > Length
unit: to "Inch".  However, the rulers still appear to display in
centimeters.  I created a new drawing and they still display in cm.
The help does not say anything about ever being able to display in
other units.

What is the meaning and purpose of File > Preferences > User Interface
tab > Length unit:?  Is it possible for the rulers to display in units
other than cm?

When I use a Network object such as Storage or Computer, using Tools >
Edit text (F2) allows an annotation label to be edited below the
object.  However, if I use a UNIX workstation, switch, or router
object, there does not appear to be a label that can be edited.  Is
this correct?  What decides if an object has a label or not?