The Role of the Viewer is developed from the study of semiotics, and semiotics is the study of signs in society. It is concerned with the process in which signs and symbols come to a meaning.
For example the word car
is the signified, which is the word in itself. It is an interpretation of the object, which is the signifier.
Following this idea Edgar created a signifier and left the signified to be created by the viewer.
The work is not complete until the viewer has complete his role.