Multimedia or Polymedia library: store information and knowledge using a wide variety of media types such as paper, microfilm, computer disks and so on. Essentially, such libraries will be very similar to conventional libraries as we know them today . . . an important aspect will be the access to human librarians as a source of expertise.
Electronic library: the core processes become basically electronic in nature (there is) a conscious movement towards the more widespread use of electronic media for the storage, retrieval and delivery of information . . . Users of this type of library will still be able to gain access to librarians but attempts will usually be made to computerise some of the more routine queries that library staff have to handle.
Digital library: the information that they embed exists only in a digital electronic format. Because of the way in which information is stored, digital libraries do not contain any conventional books. The major types of publication contained in this kind of library will be the electronic books, journals, newspapers and so on . . . special mechanisms will be needed to provide access to librarian services for example, by means of electronic mail and the emulation of the behaviour of librarians using expert system technologies.
Virtual library : depends for their existence (on) a developing area of technology known as virtual reality (VR) . . . .as well as providing access to virtual indexes, catalogues and books . . . VR libraries . . . might include surrogate travel, learning scenarios and access to virtual librarians . . .