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 business rules.