specially ordered sets variables in Mathprog

Hi,

I'd like to know whether Mathprog supports (or is there any plan to support) SOS (special ordered sets) variables, at 
least type 1.

I often use mathprog and glpsol to convert MILP problems (actually, BLP mostly) for other solvers (CBC, CPLEX), and I'm 
seeing these other solvers support these types of variables, what makes me think that there might be some advantages in 
formalizing a problem this way, as perhaps the solver might be quicker in scanning through the possible branches etc... 
I mean, using the SOS1 native formalization, instead of equivalent formulations as in

https://en.wikibooks.org/wiki/GLPK/Modeling_tips#Special_ordered_sets

Thanks,

     T.

-- 
Tommaso Cucinotta, Computer Engineering PhD
Associate Professor at the Real-Time Systems Laboratory (ReTiS)
Scuola Superiore Sant'Anna, Pisa, Italy
http://retis.sssup.it/people/tommaso