Abstract: At the information delivery server, access logs for accesses to information items made by users are managed, and a correlation detection condition indicating at least one information item is received from a client. Then, related users who made accesses to that at least one information item are detected according to the access logs, correlated information items that are accessed by the related users are extracted according to the access logs, and the correlated information items are delivered to the client.

Abstract: In a recommended item presentation server, client identifier associated client preference estimating factor information of a plurality of clients is obtained, and when a recommended item presentation request and a client preference estimating factor information of one client is received from an item provider server for providing items to a plurality of clients through a network, where the client preference estimating factor information indicates a preference of the one client, without identifying the one client, a recommended item list is produced according to the client identifier associated client preference estimating factor information and the client preference estimating factor information and transmitted to the item provider server.

Abstract: A recommended item presentation device uses the access log for viewing/purchasing items on the item provider server made by the client as the analysis source information, so that there is less burden of input on the client side and it becomes possible to collect a large amount of the analysis source information, and the rating input for each item or the list of preferred items as the user preference estimating factor information indicating the user preference, so that it becomes possible to explicitly indicate the user preference and to change it whenever necessary.