Systems of artistic genres, evaluative rankings of artists, and identifications of canonical monuments are all versions of classification and categorization. The identification of canonical objects and forms operated through evolving systems of preservation, collecting, transmission, and dissemination, involving physical monuments, institutions, texts, and publications, from early versions down to modern era museums and art-historical surveys. Category distinctions were thus historically and socially dynamic. A literature and discourse of artistic genres, concerned primarily with painting, appears in Chinese writings from the fourth through the fourteenth centuries, with varying numbers of identified genre categories, changing hierarchies of importance, and occasional accounts of the significance of particular genres. Many art writers from the sixth through the eleventh centuries ranked painters and calligraphers along qualitative scales, but such systems gave way in later eras to evaluations based on school or lineage affiliations, or on esthetic categories of critical discourse.