Politically, how was early sumerian society organized? how did that affect society?

Apparently Sumerian society was thought to be comprised of four social classes: Nobles, commoners, clients and slaves. The Nobles, who were at the top of Sumerian society, consisted of priests, warriors, and of course, the ruling family. Commoners were your average citizen of Sumer at the time. They were the farmers, and craftsmen, and blacksmiths (very, very crude form of blacksmithing). Clients and slaves were the lowest. The slaves had no rights whatsoever. Clients, however could do more and even buy their freedom. 
   This affected society by trying to create a perfect utopia it caused jealousy towards the higher class and bitterness to others, causing many revolts and outbreaks. The fact the laws were quiet strict, helped fuel that anger and hatred.