Recording medium storage hierarchical information, device, system, method, and computer program, and recording medium storing such computer program

A navigation system that can easily retrieve hierarchically stored pieces of information is provided. When an input operation requesting retrieval of destination information at an operation section (440) of a terminal unit (400) is recognized, retrieval information and item information of map information are acquired from a memory section (320) of a main server unit (300) by way of a communication section (410). Then, a retrieval form acquiring section (483) acquires a retrieval form such as a list display, a numeric keypad template, and a Japanese alphabet template according to the retrieval information to be used to acquire item information stored in different layers of hierarchy so that a display section (450) displays the acquired form. Ultimately, the display section (450) displays POI data located in the lowest layer of hierarchy. Since the item information that is hierarchically stored is associated with retrieval information corresponding to a retrieval form for retrieving the item information, the system can accommodate operations using different pieces of retrieval information to retrieve required item information.