Yasuhiko Kanemasa

Fat-Btree: an update-conscious parallel directory structure

We propose a parallel directory structure, Fat-Btree, to improve high speed access for parallel database systems in shared nothing environments. The Fat-Btree has a threefold aim: to provide an indexing mechanism for fast retrieval in each processor; to balance the amount of data among distributed disks, and to reduce synchronization costs between processors during update operations. We use a probability based model to compare the throughput and response time of the Fat-Btree with two ordinary parallel Btree structures, with copies of a whole Btree in each processor and storing index nodes in a processor. The comparison results indicate that the Fat-Btree is suitable for actual parallel database systems that accept update operations.

Document warehousing based on a multimedia database system

Nowadays, structured data such as sales and business forms are stored in data warehouses for decision makers to use. Further, unstructured data such as emails, HTML texts, images, videos, and office documents are increasingly accumulated in personal computer storage due to spread of mailing, WWW, and word processing. Such unstructured data, or what we call multimedia documents, are larger in volume than structured data and precious as corporate assets as well. So we need a document warehouse as a software framework where multimedia documents are analyzed and managed for corporate-wide information sharing and reuse like a data warehouse for structured data. We describe a prototype document warehouse system, which supports management of simple and compound documents, keyword-based and content-based retrieval, rule-based classification, SOM-based clustering, and XML data query and view rules.