The implementation of the Amsterdam SGML parser
Electronic Publishing—Origination, Dissemination, and Design
The SGML handbook
Regular expressions into finite automata
Theoretical Computer Science
From structured documents to novel query facilities
SIGMOD '94 Proceedings of the 1994 ACM SIGMOD international conference on Management of data
The SGML implementation guide: a blueprint for SGML migration
The SGML implementation guide: a blueprint for SGML migration
One-unambiguous regular languages
Information and Computation
Markup Languages
Theory of Computation: A Primer
Theory of Computation: A Primer
Developing SGML DTDs: From Text to Model to Markup
Developing SGML DTDs: From Text to Model to Markup
PODP '96 Proceedings of the Third International Workshop on Principles of Document Processing
Unambiguity of Extended Regular Expressions in SGML Document Grammars
ESA '93 Proceedings of the First Annual European Symposium on Algorithms
The validation of SGML content models
Mathematical and Computer Modelling: An International Journal
On predictive parsing and extended context-free grammars
Computer Science in Perspective
Enforcing strict model-view separation in template engines
Proceedings of the 13th international conference on World Wide Web
Deciding determinism of caterpillar expressions
Theoretical Computer Science
On predictive parsing and extended context-free grammars
CIAA'02 Proceedings of the 7th international conference on Implementation and application of automata
Deterministic caterpillar expressions
CIAA'07 Proceedings of the 12th international conference on Implementation and application of automata
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The Standard Generlized Markup Language (SGML) and the Extensible Markup Language (XML) allow users to define document-type definitions (DTDs), which are essentially extended context-free grammars expressed in a notation that is similar to extended Backus-Naur form. The right-hand side of a production, called a content model, is both an extended and a restricted regular expression. The semantics of content models for SGML DTDs can be modified by exceptions (XML does not allow exceptions). Inclusion exceptions allow named elements to appear anywhere within the content of a content model, and exclusion exceptions preclude named elements from appearing in the content of a content model. We give precise definitions of the semantics of exceptions, and prove that they do not increase the expressive power of SGML DTDs when we restrict DTDs according to accepted SGML practice. We prove the following results: 1. Exceptions do not increase the expressive power of extended context-free grammars. 2. For each DTD with exceptions, we can obtain a structurally equivalent extended context-free grammar. 3. For each DTD with exceptions, we can construct a structurally equivalent DTD when we restrict the DTD to adhere to accepted SGML practice. 4. Exceptions are a powerful shorthand notation---eliminating them may cause exponential growth in the size of an extended context-free grammar or of a DTD. Copyright 2001 Academic Press