SF and DUP can't work together
As a result of the Good Friday Agreement of 1998, I guess it was only human nature that the nationalist community would hide behind the extreme left-wing party that is Sinn Fein and similarly the unionist community behind the extreme right-wing Democratic Unionist Party as an insurance against a relapse into civil war.
Clearly this coalition can not be sustained indefinitely. It is like having a government comprising of a Stalinist Soviet Union and a George Bush America.
The sooner parties of the nature of the Ulster Unionist party and the SDLP regain the common middle ground, the sooner a more realistic form of government will prosper.