SGML

Introduction

• SGML stands for ‘Standard Generalized Markup Language’.
• SGML was first published as an international standard in 1986 (ISO 8879:1986) by the International Organization for Standardization (ISO).
• Despite being less prevalent in modern usage, SGML remains an important milestone in the evolution of markup languages and document processing technologies. 

Definition

• SGML provides a powerful framework for defining and structuring electronic documents, enabling organizations to create, manage, and exchange structured information in a standardized and interoperable manner.
• SGML is a standard for defining markup languages, which are used to annotate or mark up electronic documents to describe their structure and content.
• SGML provided a foundational framework for the development of modern markup languages and structured document formats, influencing the design of subsequent standards and technologies for encoding, managing, and exchanging structured information.

Characteristics

• Historical/Legacy Significance:
  • SGML laid the foundation for the development of other markup languages, including HTML (Hypertext Markup Language), XML (Extensible Markup Language), and XHTML (Extensible Hypertext Markup Language).
  • While SGML itself is less commonly used today, its principles and concepts continue to influence the design of modern markup languages and document formats. Thus, it played a significant role in the development of other markup languages, including HTML (Hypertext Markup Language), XML (Extensible Markup Language), and XHTML (Extensible Hypertext Markup Language).
• Markup Language Definition:
  • SGML provides a framework for defining markup languages by specifying rules for structuring documents, defining document elements, and specifying how elements should be marked up using tags and attributes.
  • SGML is designed to be highly flexible and customizable, allowing users to define their own document types and markup vocabularies.
• Document Structure:
  • SGML separates the structure of a document from its presentation by defining the logical elements and relationships that make up the document’s content.
  • Documents encoded in SGML consist of nested elements, each marked up with start and end tags to denote their boundaries.
• Document Type Definitions (DTDs):
  • SGML documents are typically accompanied by Document Type Definitions (DTDs), which define the structure and constraints of the markup language used in the document.
  • DTDs specify the allowable elements, their attributes, and the rules governing their arrangement within the document.
• Content Reuse and Interchange:
  • SGML enables content reuse and interchange by allowing documents to be composed of reusable components called entities. Entities can represent text fragments, graphics, tables, or other elements, which can be included, referenced, or reused within multiple documents.
• Platform-Independent:
  • SGML is platform-independent and can be used to create documents that are portable and interoperable across different systems, applications, and environments.
  • SGML documents can be parsed, processed, and rendered by SGML-aware software tools and applications.

Industry Use/Applications

• GML has been widely used in various industries, including publishing, documentation, aerospace, defense, data interchange, and government, where structured documentation and information interchange are critical.