An intelligent interface for an information retrieval system has the
aims of controlling an underlying information retrieval system,
directly interacting with the user, and allowing him to retrieve
relevant information without the support of a human intermediary.
Developing intelligent interfaces for information retrieval is a
difficult activity, and no well established models of the functions
that such systems should possess are available. Despite of this
difficulty, many intelligent interfaces for information retrieval have
been implemented in the past years.  This paper surveys these systems,
with two aims: to stand as a useful entry point for the existing
literature, and to sketch an analysis of the functionalities that an
intelligent interface for information retrieval has to possess.