A method and apparatus are provided for transferring a resource from the cache of one database server to the cache of another database server without first writing the resource to disk. The current source provides a first current, a second current, and a third current, which are equal to one another. Each of the sub-buses is connected to one of the circuit chips. The cliques are clustered to generate named entity groups on the basis of mutual similarity of the contexts of the named entities constituting the cliques.