Patent US 5,404,512

The subject invention is directed to a database system for organizing large amounts of data to be accessed by a digital computer. More particularly, a free form type database, in the form of a summarized, multikey tree, is built from files stored on the computer. After a building operation, the user obtains specified information by using the summarized database. Information in the files is divided into three categories; that is, a dimension field which comprises data to be organized, a summary field which comprises a numeric quantity on which calculations can be performed, and a non-summary field which comprises other information associated with an input record. The internal nodes of the tree summarize and organize sets of input records. Methods are provided for reducing the amount of storage space used by cutting off the tree when the size of sets go below a given threshold, and sharing parts of the tree so that each record does not appear n! times in the database.