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There is an increasing demand for efficient indexing techniques to support queries on large string databases. In this paper, a hybrid RAM/disk-based index structure, called the Hybrid Digital tree (HD-tree), is proposed. The HD-tree keeps internal nodes in the RAM to minimize the number of disk I/Os, while maintaining leaf nodes on the disk to maximize the capability of the tree for indexing large databases. Experimental results using real data have shown that the HD-tree outperformed the Prefix B-tree for prefix and substring searches. In particular, for distinctive random queries in the experiments, the average number of disk I/Os was reduced by a factor of two to three, while the running time was reduced in an order of magnitude. [ABSTRACT FROM AUTHOR]

The implementation of information systems in organizations is a long standing research topic that has preoccupied researchers ever since computer-based information systems started being used in businesses in the early 1960s. However, despite more than 40 years of research, the implementation phenomenon continues to present both practical and research difficulties. The present paper presents a broad overview and assessment of past and current research on implementation, and provides suggestions for future research that will help address some of the challenges implementation researchers currently face. [ABSTRACT FROM AUTHOR]