Authenticity in art has a variety of meanings related to different ways in which a work of art or an artistic performance may be considered authentic. Denis Dutton distinguishes between nominal authenticity and expressive authenticity. The first refers to the correct identification of the author of a work of art, to how closely a performance of a play or piece of music conforms to the author’s intention, or to how closely a work of art conforms to an artistic tradition. The second sense refers to how much the work possesses original or inherent authority, how much sincerity, genuineness of expression, and moral passion the artist or performer puts into the work. A quite different concern is the authenticity of the experience, which may be impossible to achieve. A modern visitor to a museum may not only see an object in a very different context from that which the artist intended, but may be unable to understand important aspects of the work. The authentic experience may be impossible to recapture. Authenticity is a requirement for inscription upon the UNESCO World Heritage List. According to the Nara Document on Authenticity, it can be expressed through ‘form and design; materials and substance; use and function; traditions and techniques; location and setting; spirit and feeling; and other internal and external factors.’