A file organization for cluster-based retrieval

A file organization for cluster-based retrieval is presented and tested. This file organization is based on the bottom-up search which, in contrast to the more usual top-down search, starts at the lowest level of a cluster hierarchy (the documents) and looks at progressively larger clusters. This approach enables most of the efficiency problems previously associated with clustered file organizations to be avoided. There are two parts to this file organization - a compact cluster hierarchy representation which does not store cluster representatives and a compact inverted file which is used to provide a starting point for the bottom-up search. Retrieval experiments show that the bottom-up search using this file organization can be more effective than a serial search, especially if high precision results are required.