Information:  - Endogamy is the practice of marrying within a specific ethnic group, class, or social group, rejecting others on such a basis as being unsuitable for marriage or for other close personal relationships.  - Caste is a form of social stratification characterized by endogamy, hereditary transmission of a lifestyle which often includes an occupation, status in a hierarchy, and customary social interaction and exclusion. Its paradigmatic ethnographic example is the division of Indian society into rigid social groups, with roots in India's ancient history and persisting until today. However, the economic significance of the caste system in India has been declining as a result of urbanization and affirmative action programs. A subject of much scholarship by sociologists and anthropologists, the Indian caste system is sometimes used as an analogical basis for the study of caste-like social divisions existing outside India. The term is also applied to non-human populations like ants and bees.  - The Pasi are one of the untouchable communities ( or dalits ) who are now classified as a Scheduled Caste under modern India 's system of positive discrimination . As untouchables , they were traditionally considered outside the Hindu ritual ranking system of castes known as varna . They live in the northern Indian states of Bihar and Uttar Pradesh .  - Social stratification is a society's categorization of people into socioeconomic strata, based upon their occupation and income, wealth and social status, or derived power (social and political). As such, stratification is the relative social position of persons within a social group, category, geographic region, or social unit. In modern Western societies, social stratification typically is distinguished as three social classes: (i) the upper class, (ii) the middle class, and (iii) the lower class; in turn, each class can be subdivided into strata, e.g. the upper-stratum, the middle-stratum, and the lower stratum. Moreover, a social stratum can be formed upon the bases of kinship or caste, or both.  - The caste system in India is the paradigmatic ethnographic example of caste. It has origins in ancient India, and was transformed by various ruling elites in medieval, early-modern, and, modern India, especially the Mughal Empire and the British Raj. It is today the basis of educational and job reservations in India. It consists of two different concepts, "varna" and "jti", which may be regarded as different levels of analysis of this system.  - Affirmative action (known as reservation in India and Nepal and positive discrimination in the UK; also known in a narrower context as employment equity in Canada and South Africa) is the policy of favoring members of a disadvantaged group who suffer or have suffered from discrimination within a culture. Often, these people are disadvantaged for historical reasons, such as oppression or slavery. Historically and internationally, support for affirmative action has sought to achieve goals such as bridging inequalities in employment and pay, increasing access to education, promoting diversity, and redressing apparent past wrongs, harms, or hindrances. The nature of affirmative action policies varies from region to region. Some countries, such as India, use a quota system, whereby a certain percentage of government jobs, political positions, and school vacancies must be reserved for members of a certain group. In some other regions where quotas are not used, minority group members are given preference or special consideration in selection processes.    Given the information, choose the subject and object entities that have the relation of 'instance of'.
pasi  , ethnic group