Abstract: An apparatus and method for restructuring a database modeled by an edge-labeled tree. Portions of an output tree is generated by matching patterns of tree elements of a starting tree. Portions of the output tree are combined to form a complete output tree which may be restructured again until a final output tree presents a desired "view" of the starting database. If the pattern matches used in restructuring the starting tree is restricted to attributes of tree elements that only includes preceding edge information, successive tree restructuring may be composed into a single restructuring process that optimizes the restructuring by taking advantage of restructuring results of each of the original restructuring processes.

Abstract: A database access system responds a user database access request by restructuring a requested database based on two sets of expressions. Expressions are instructions for generating a new database from a starting database modeled as a starting edge-labeled tree by using pattern matches. Expressions always generate an edge-labeled tree allowing a sequence of expressions to be processed to restructure the starting tree. The database access system divides the database restructuring process into two sets of expressions. A first set of expressions is constructed based on subscriber requirements and a second set of expressions is constructed based on particular user requests. The first and second expressions are optimized by composition and the requested database is restructured based on the composed expression.