In the medieval Serbian states, the privileged class consisted of nobility and clergy, distinguished from commoners, part of the feudal society. The Serbian nobility (srpska vlastela, srpsko vlastelinstvo or srpsko plemstvo) were roughly grouped into magnates (velikaši or velmože), the upper stratum, and the lesser nobility (vlasteličići). Serbia followed the government model established by the Byzantine Empire. The nobility possessed hereditary allodial estates, which were worked by dependent sebri, the equivalent of Byzantine paroikoi; peasants owing labour services, formally bound by decree. The nobility was obliged to serve the monarch in war. Hierarchy The nobility (vlastela, vlastelinstvo or plemstvo) of Serbia in the Middle Ages is roughly divided into magnates (velikaši or velmože), nobility and petty noblemen (vlasteličići). Sometimes, the division is made between vlastela (including "great" and "small" ones) and vlasteličići, the petty nobility. The lower-half social class, commoners, were the sebri (себри). The velikaši (великаши) were the highest nobility class of Serbia. The vlasteličići (властеличићи) were the lower nobility class of Serbia. It was a relatively numerous class of the small, warrior nobility, originating from the vojnici (warriors) from sources from the end of the 12th and the beginning of the 13th century. They held villages, with full rights, and in socioeconomic and legal terms stood below the vlastela. They had military obligations, such as the vlasteličić joining the army individually or with a group of his men (soldiers), dependent on his wealth. Titles History Early Medieval Serbian principalities The Serbs at that time were organized into župe (sing. župa), a confederation of village communities (roughly the equivalent of a county), headed by a local župan (a magistrate or governor); the governorship was hereditary, and the župan reported to the Serbian prince, whom they were obliged to aid in war. According to Fine Jr.: Bosnia, Zahumlje and Rascia were never incorporated into an integrated state with Duklja (1043–1101); each principality had its own nobility and institutions, simply requiring a member of the royal family to rule as Prince or Duke. After Constantine Bodin died, the principalities seceded from Duklja, and Vukan became the most powerful Serb ruler, as Grand Prince. Subordinate to the ruler were local counts who seem to have been more or less autonomous in the internal affairs of their counties, but who swore loyalty and were obliged to support in war. It seems that the counts were hereditary holders of their counties, holding their land