Some cultural phenomena gain wide popular appeal, and others do not. Some appeal to certain age groups or social classes. Some, such as rock and roll, jazz, and classical music, are popular worldwide; other cultural forms, such as Tejano, salsa, and Cajun music, are popular primarily in certain regions or ethnic communities. Certain aspects of culture are considered elite in one place (e.g., opera in the United States) and popular in another (e.g., opera in Italy). Though categories may change over time and from one society to another, two metaphors offer contrasting views about the way culture operates in our daily lives: culture as a hierarchy, represented by a skyscraper model, and culture as a process, represented by a map model.