Extending SGML to accommodate database functions: A Methodological Overview

Abstract

A method for augmenting an SGML document repository system with database functionality is presented. SGML (ISO 8879, 1986) has been widely accepted as a standard language for writing text with added structural information that gives the text greater applicability. Recently there has been a trend to use this structural information as metadata in databases. The complex structure of docuuments, however, makes it difficult to directly map the structural information in documents to database structures. In particular, the flat nature of relational databases makes it extremely difficult to model documents that are inherently hierarchical in nature. Consequently, documents are modeled in object-oriented databases (Abite-boul, Cluet, & Milo, 1993), and object-relational databases (Holst, 1995), in which SGML documents are mapped into the corresponding database models and are later reconstructed as necessary. However, this mapping strategy is not natural and can potentially cause loss of information in the original SGML documents. Moreover, interfaces for building queries for current document databases are mostly built on form-based query techniques and do not use the â â look and feelâ â of the documents. This article introduces an implementation method for a complex-object modeling technique specifically for SGML documents and describes interface techniques tailored for text databases. Some of the concepts for a Structured Document Database Management System (SDDBMS) specifically designed for SGML documents are described. A small survey of some current products is also presented to demonstrate the need for such a system.