HyperFile, a Database Manager for Documents

Documents, pictures, and other such non-quantitative information pose interesting new problems in the database world. Such data has traditionally been stored in file systems, which do not provide the security, integrity, or query features of database management systems. We have developed HyperFile, a data server that provides query facilities (as well as some other database features) while maintaining the flexibility and efficiency of a file system. HyperFile is based on the hypertext notion of free-form objects connected by links. Hypertext systems “query” their database by browsing (reading objects and following links.) We present a query interface that maintains much of the flavor of browsing, allowing the user to specify a single query rather than manually following links. This eliminates the repeated user interactions of hypertext browsing, and allows the hypertext model to be extended to larger and less structured databases. An algorithm for processing HyperFile queries is presented. We also show how to extend this algorithm for distributed query processing, and present experimental results from a distributed HyperFile server. Another issue explored is indexing. In HyperFile, searches are often demarcated by pointers between items. Thus the scope of the search may change dynamically, whereas traditional indexes cover a statically defined region such as a relation. This demands new indexing techniques. Some ideas on indexing in HyperFile are presented, as well as experiments in a large HyperFile database. Also presented is a sample HyperFile application. This is a “browser” that uses menus to guide the user in constructing HyperFile queries.