Design of an External Schema Facility to Define and Process Recursive Structures

Abstract

The role of the external schema is to support user views of data and thus to provide programmers with easier data access. This author believes that an external schema facility is best based on hierarchies, both simple and recursive. After a brief introduction to an external schema facility to support simple hierarchical user views, the requirements for a facility for recursive hierarchies are listed and the necessary extensions to the external schema definition language are offered.Functions that must be provided for generality in definition are node specification and node control. Tree traversal functions must be provided for processing. Definitions of each and examples of use are presented. © 1981, ACM. All rights reserved.