Abstract: This document is the report for Phase III of an investigation into the application of hierarchical data structures to geographical information systems. It deals primarily with enhancements and improvements to the information system package described in the Phase II report (University of Maryland TR-1327), an evaluation of design decisions, and the collection of empirical results to indicate the utility of the software and justify the design decisions. Tasks reported on include: Attribute attachment, DMA SLF compatibility, memory management improvements, and database enhancements.