The Visual Works hierarchy contains terms for items, including works of art and any objects that occupy space, are perceived by the sense of sight, and are created, rather than naturally occurring. This hierarchy focuses especially on works conveying a symbolic or expressive meaning or an aesthetic experience, such as pictorial and sculptural works, and time-based works such as performance art. Relation to other hierarchies: In the Information Forms hierarchy are terms for items that communicate by visual, nonverbal means, but whose purpose is primarily informational (e.g., "maps"). Terms for decorative elements are in the Design Elements hierarchy (e.g., "scrollwork") and the Components hierarchy (e.g., "acroteria"); architectural forms that are primarily structural and secondarily sculptural (e.g., "caryatids") also appear in Components. Most terms used to create works are in the Materials hierarchy (e.g., "canvas"), although if found objects are used (e.g., "dinner plates"), these are considered components of the work, not materials. Terms for the methods used to create a work (e.g., "wet collodion process," "carving") are in the Processes and Techniques hierarchy.