What constraint should I use?

I’m currently working on import and export for The Movies .msh format and I’m a little stuck on constraints. The data I have available is in the following format:

For each bone I have the head co-ordinates and 3 sets of offsets that give the tail co-ordinates for rest position, min position and max position.

The closest constraint I can find is the action one, but I can’t seem to find current documentation on the “Local” option to see if that will let me constrain the tail based on the bones own head (or rest) position.

In psuedo code, I need to do something like:

(head_x + x_min) <= tail_x <= (head_x + x_max)

Any pointers would be much appreciated.

Current status of the import and export routines is at http://www.tmws.themoviesplanet.com/forum/viewtopic.php?t=617

The completed routines will be released under the GPL license.

How about setting up named poses for each constraint position?
Then you can set each pose on a specific frame, go to that frame to read the pose and its coordinates.

If there isn’t currently a way to do the constraints properly, I will be doing something like that or maybe just hard coding defaults for full range of motion. With this I’m thinking ahead to being able to add new animations to The Movies, in which case having a properly constrained “actor” will be very useful.

Right, I can see that. For sets, would I be right to think that the constraint values are 0?

Some notes on Constraints:

https://blenderartists.org/forum/viewtopic.php?t=58734&highlight=constraint

http://en.wikibooks.org/wiki/Blender_3D:_Noob_to_Pro/Advanced_Tutorials/Advanced_Animation/index

Constraint tutorial.

http://www.malefico3d.com.ar/tutor/mecano-en.html