xform rotations based on euler not fixed axis

[Mathew Schwartz]

I seem to not understand how xform works, so help is appreciated.

Given an object located at the center, using:

cmds.xform(ro=(10,20,0),roo = 'xyz', ws= True,eu=False)

I would expect the object to use world space orientation, and use fixed axis instead of euler.  This works.  However, the opposite does not hold:

cmds.xform(ro=(10,20,0),roo = 'xyz', os= True,eu=True)

I would imagine the object should be rotating on the object axis 10 degrees on x axis, then, by using euler rotation, use the new object axis to rotate 20 on y.  However, it just does the same thing as the first situation.

How can I use object space and euler rotation with this, and what is maya doing?

Thanks,

Mat