A database system is provided with a search unit for searching image
attribute information that has been stored in a relational database
management system. A search interface is provided between the search unit
and a command execution unit, which applies a search command to the
search unit. The command execution unit and search unit can be connected
in detachable fashion. Thus a search unit that has been connected to the
command execution unit can be replaced by detaching it and connecting a
search unit that employs another search technique.