Database system with query relaxation using type abstraction hierarchy (TAH) as query condition relaxation structure

摘要

A system for obtaining target data from a conventional computer database in response to an input query which has at least one attribute includes a Type Abstraction Hierarchy (TAH) manager for providing a TAH structure including relaxation conditions for said at least one attribute. A control unit successively applies a database query which corresponds to the input query to and receives data from the database, with progressively relaxed conditions of the attribute(s) being provided by the TAH manager, until the target data in the form of a specified number of ranked answers which satisfy the attribute conditions is obtained. The attribute relaxation process can be controlled such as relaxation order, preference list, reject, etc. to obtain user and context specific answers. The system can produce approximate answers or answers to query with conceptual terms. The input query can including cooperative operators such as "APPROXIMATELY", "NEAR TO" or "SIMILAR TO" or conceptual terms (e. g. "long"), which the conventional database is not capable of directly processing. The control unit converts the cooperative operators and conceptual terms into database operator which the database is capable of processing. The TAH structure includes TAHs having leaves corresponding to instances of the attributes respectively, and a hierarchical arrangement of nodes that specify ranges which include at least one of the instances respectively. The instances can be numerical and/or non- numerical. The nodes can be defined by conceptual names (terms) that describe the instances under that node (e.g. dark color, long runway).