An apparatus consisting of a networked data storage device and a software system for automatically indexing the data on the storage device by topic, and for sharing both the data and the topic indexes on the network. These may be used to provide the user of the apparatus with functionality including, but not limited to, content-based searching, sharing and automatic recommendations. The storage device stores its data by means of a file system. The indexing portion of the software performs topic-based categorization by means of a higher-order path analysis algorithm, which mimics human intuition by considering both high- and low-order links between data elements. The indexes generated by the software arc automatically partitioned by topic. The indexing software operates continuously and transparently, updating the index as data is added to or removed from the storage device.