Structure and Redundancy in the Conceptual Schema in the Administration of Very Large Data Bases
Herbert S. Meltzer · Very Large Data Bases · 1976
This presentation explains the role of the conceptual schema in securing management control over very large data bases and in providing data independence for users of the data. The ccnceptual schema can also be used to describe the information model of an enterprise. The conceptual schema is presented as a tool of data base administration. This presentation addresses structure and redundancy in the conceptual schema. Two philosophies exist concerninq permissible mappings between an external schema and the conceptual schema. One, to provide maximum derivability of information from the data, assumes an unstructured, non-redundant conceptual schema, third normal conceptual record sets, and permits arbitrarily structured external records to be defined in terms of combinations of conceptual records. The other, to provide dynamic data independence during attribute migration and control over the information that can be derived from the data, assumes a highly structured, highly redundant conceptual schema, third normal,...,unnormalized conceptual record sets, and requires external records to be subsets of predefined conceptual records. A complete data base management system should provide both capabilities, and enforce constraints when each may be used.