Abstract: A distributed computer system has computers storing data items each data item being assigned to one of a plurality of virtual directories. Each computer has at least one node of a virtual network (10) for directory look-up, with linking data comprising addresses of other nodes associated with the same virtual directory and software that, in response to an enquiry message either replies, identifying itself or forwards the message to another node of the network (10), according to whether the node is or is not associated with the directory specified in the enquiry message. Similarly, each computer has, for each item that it stores, a node of a virtual network for item look-up, with linking data comprising addresses of other such nodes associated with items assigned to the same virtual directory, so that these linking data together define a plurality of virtual networks for item look-up, each of which networks corresponds to a respective different virtual directory.

Abstract: A virtual network has a plurality of nodes, each node with a list for storing up to a predetermined number (L) of addresses representing links to other such nodes.

Abstract: Nodes of a computer network are found by performing, in response to input of a label, a first retrieval operation (32) to identify the address of a node matching that label, and performing, in response to an address identified by the first retrieval means, a second retrieval operation (35) to identify the addresses of further nodes matching the same label. Each node matching a given label has a data storage area for containing the addresses of other nodes matching the same label and is responsive to enquiry messages to return a message containing the addresses of the list. The second retrieval operation includes sending an enquiry message to the address identified by the first retrieval means and upon receipt of a response iteratively sending further enquiry messages to addresses contained in the response to the previous enquiry message.

Abstract: A browsing process is driven by user interaction. The user is presented with a selection of items 511, 512, . . . etc from a range. The user can give inputs representing interest in one or other of the items displayed. The inputs represent rewards, which are distributed to attribute data items or “keywords” associated with the display items. These keywords are transparent to the user, but represent characteristics of the display items with which they are associated. The browsing system selects items for display according to a probabilistic function weighted to favour those having the keywords which have accrued the highest number of rewards, these being the display items having the most keywords in common with display items previously rewarded by the user during the browsing session. Partial or negative weightings may also be applied to the keyword associations, which are also taken into account in the selection process.