Cluster-skipping IIS (CS-IIS) as a data structure for efficient information retrieval in flat clustered environments has been recently proposed. In this project, we go one step further and plan to adapt this data structure to hierarchical clustering environments, implement and evaluate the performance of update operation on this data structure for flat and hierarchical clustering environments, implement a parallel IR system that employs this data structure and obtain and use several test datasets (from DMOZ site and other Web directories, including Turkish directory sites) for extensive performance evaluation.