Four French hostages are now back in France after 10 months in captivity in Syria. Edouard Elias, Didier François, Nicolas Henin and Pierre Torres were welcomed back on the tarmac of a military airport near Paris by French President François Hollande and Foreign Minister Laurent Fabius. On the ground in Syria, meanwhile, the date for the next presidential election has been announced. But exactly who will be able, or allowed, to vote in the middle of a 4-year-old civil war?