The emergence of the Internet, however, has led to the adoption of electronic catalogue databases (often referred to as "webcats" or as online public access catalogues, OPACs), which allow users to search the library's holdings from any location with Internet access. This style of catalogue maintenance is compatible with new types of libraries, such as digital libraries and distributed libraries, as well as older libraries that have been retrofitted. Large libraries may be scattered within multiple buildings across a town, each having multiple floors, with multiple rooms housing their resources across a series of shelves called bays. Once a user has located a resource within the catalogue, they must then use navigational guidance to retrieve the resource physically, a process that may be assisted through signage, maps, GPS systems, or RFID tagging.