Semiotics is of central importance to twentieth century literary theory, growing out of structuralism. The lilac breasted roller perched on the sign post aptly signifies both semiotics and the Vault emblem.
This link takes you to an online and open introduction to semiotics. It is strongly recommended as preparatory reading for the THL 2601 module: Theory of the sign in literature and culture.
This link shows how the structuralist concepts of metaphor and metonymy can be used to analyse ancient rock art.
