I have questions about a very specific boundary condition which I am trying to implement. 

For UnsteadyAdvectionDiffusion case, consider 3 fields - u1,u2 and u3. For u1, I have Robin bc with "Value" dependent on values of u2 and u3. 

I tried the following: I made the robin bc time dependent in order to force it to evaluate at each timestep. Then to enforce the "Value" part, I have to write solutions for u2 and u3 in a file ".bc" and load it up at each evaluate call for u1's robin bc. I was looking into examples to do this but could only find information about how to make the bcs load from file. The *.bc files in test folder of ADRSolver are compressed versions. It would be helpful if you could point me out to:

1. How to expand the *.bc file from given test examples

2. How to write out solutions for u2 and u3 at each timestep to a .bc file which u1 will utilize in next timestep

3. Is there a better way to do this?

Thanks !
--