The HyTime Technical Corrigendum - Part I

(C)Copyright 1996 Charles F. Goldfarb. All rights reserved.

Primary Objectives

• Correct several known minor problems
• Distinguish general rules for defining architectures from their use in defining HyTime architecture
• Eliminate ambiguities in property sets, parsing context and their impact on location addressing
• Correct flaw in sbento design

Additional Objectives

• Alignment with DSSSL
  • Query Language (HyQ -> SDQL)
  • Expression language (HyOP + HyFunk -> DSSSL)
  • Model of parsed SGML (Groves)
• Integrated 2nd edition
• Test ISO/CS SGML publishing system

SGML Extended Facilities

• General applicability to SGML
• HyTime architecture is not required
• Definition requirements for
  • Architectural Forms (AFDR)
  • Property Sets (PSDR)
  • Formal System Identifiers (FSIDR)
• General Facilities Architecture
• Modular conformance : use any or all

Architectural Form Definition Requirements (AFDR)

• Define "enabling architectures" for SGML documents
• Element type, attribute and notation forms
• Permits common processing tools across multiple document types
• Documents are "derived" from architectures.
• Multiple derivation levels and/or bases

History of Architectural Forms

• 1984: SGML music standard proposed to ANSI
• 7/86: SMDL work begins (Goldfarb meets Newcomb)
• 6/89: HyTime split from SMDL
  • Two DTDs connected by scores of parameter entities
• 6/90: Goldfarb proposes architectural forms
• 1990: HyTime becomes an architecture

Key AFDR Concepts

• Client document is "derived" from one or more "base" architectures (meta-DTDs)
• Client identifies its base architectures via "architecture support declarations"
• Any DTD can be a meta-DTD (even a derived DTD).
• An SGML parser can recognize "architectural instances" (as well as normal document instance)

Meta-DTD Syntax

• Conventional Comments
  • Reftype
  • Lextype
• ATTLIST Declaration Extensions
  • Multiple ATTLIST declarations permitted for same element type
  • Single ATTLIST declaration can apply to all element types
• Planned for ISO 8879 revision

Other AFDR Features

• Notation Set Architecture
  • Allow data attributes on start tags
  • Notation text in content or attributes
• Processing link architectures
  • Association via link rules

Architecture Status

• Usable today for information modeling
  • HyTime is an architecture
  • Provides OOPS-like features for data
  • Transparent to normal SGML parsing
• Initial implementation in James Clark's SP
  • Parses architectural instances
  • Many markup minimization features
  • Use with existing DTDs (e.g. HTML)

Famous AFDR Quotation

"I never meta-DTD I didn't like" -- Norm Scharpf, 11/20/96

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