I have a few questions about setting up the navigation stack. I have a very
simple simulator node which broadcasts Odometry messages and consumes Twist
messages. Using a GUI program, I've been able to monitor and verify the
performance of this node.

Assuming that for the purposes of getting started, I don't (yet) care about
mapping or obstacle-avoidance, is this simulation enough to run the
navigation stack?

I've followed the tutorials as best I can, but of course I haven't got a
map, so map_server fails to start, and then move_base gives this warning:

[ WARN] 1275592139.432109000: Waiting on transform from base_link to /map to
become available before running costmap, tf error: Frame id /base_link does
not exist!

This is expected, as I have not broadcasted any tf transforms. But my robot
has no joints or geometric parts, so there's nothing to broadcast---as far
as the simulator is concerned, it's just a box on wheels. Is there a way to
make the base_link frame exist independent of using
a tf::TransformBroadcaster to broadcast its relationship to another frame?

Further to that, how do I address the larger map issue? Can I disable the
mapping functionality somehow (for now), or should I just create a blank map
and let it use that?

Is my objective completely unreasonable, or is this just a matter of some
configuration tweaks?

Thanks in advance for any suggestions or guidance,

Mike