## Text Encoding Initiative

### The XML Version of the TEI Guidelines

# Appendix C2. Introductory Note (June 2001)

Up: Appendix C Prefatory Notes Previous: Appendix C1. Introductory Note (November 2001) Next: Appendix C3. Introductory Note (May 1999)

This is a preliminary version of a revised and fully XML-compliant edition of the TEI Guidelines. Although work on revising and correcting the text of the document is incomplete, by making available this preliminary version we hope to facilitate testing of the XML document type declarations which it describes by as wide a range of TEI users as possible.

The primary goal of this revision is to make available the corrected (May 1999) edition of the Guidelines in a new version which:

- is expressed in XML and itself conforms to a TEI-conformant XML DTD;
- generates a set of XML DTD fragments that can be combined together in the same way as the existing TEI (P3) SGML DTD fragments to form true TEI XML DTD fragments without loss of functionality;
- can be processed and maintained using readily available XML tools instead of the special-purpose ad hoc software originally used for TEI P3.

As noted elsewhere, a number of errors were corrected in the May 1999 edition. A (much) smaller number of errors have also been corrected in this edition, but no new material has been added. We expect the expansion and modification of the Guidelines to become a real possibility in the context of the newly formed TEI Consortium, which has funded the preparation of this present edition.

A major design goal of both this and the previous revision has been to ensure that the DTD fragments generated would not break existing documents: in other words, that any document conforming to the original TEI P3 SGML DTD would also conform to the new XML version of it. Although full backwards compatibility cannot be guaranteed, we believe our implementation is consistent with that goal.

In making this new version, we relied extensively on preliminary work carried out by the outgoing North American editor of the TEI Guidelines, Michael Sperberg-McQueen. In a TEI working paper written in 1999, TEI ED W69, Michael sketched out a precise blueprint for the conversion of the TEI from SGML to XML, which we have implemented, with only slight modification. The current TEI editors wish to express here our admiration for the detailed care put into that paper, without which our task would have been forbiddingly difficult, if not impossible. We would also like to express our thanks to Sebastian Rahtz of Oxford University Computing Services, for his invaluable assistance in preparing this new edition.

We list here in summary form all the changes made in the present edition. Full technical details are provided in documents TEI EDW69 and TEI EDW70, available from the TEI website.

- A new keyword TEI.XML has been added. By setting its value to `INCLUDE`, rather than the default `IGNORE`, the user can request generation of an XML rather than an SGML DTD;
- The content models of all elements have been checked, and, where necessary, changed so that they are equally valid as SGML or as XML;
- The declared value for all attributes has been changed to a form which is equally valid as SGML or as XML;
- All the examples have been checked for conformance and converted to use XML syntax, where possible. (This process is currently incomplete.)
- Some errors and duplications in the class membership of elements from the names and dates tagsets have been corrected.

To implement the first of these, we have parameterized the tag omissibility indicators ‘- o’ and ‘- -’ used within element declarations in the DTD. When XML is to be generated, the parameter entities concerned are redeclared with the null string as their value.

The second change was achieved by removing SGML-specific features (ampersand connectors, inclusion and exclusion exceptions, various types of attribute content) from the DTD and revising the syntax of the DTD to conform to XML requirements (specifically in the representation of mixed-content models, and by removing redundant parentheses). In making these changes, we took care to ensure that the resulting content model would continue to accept existing valid documents, though in the nature of things it could not be guaranteed to reject the same set of documents. As further discussed in EDW69 and EDW70, some constraints (exclusion exceptions, for example) which could be carried out by a generic SGML parser using TEI P3 will have to be implemented by a special purpose TEI validator using TEI P4.

Much work remains to be done, firstly in testing the new DTD fragments against as wide a range of TEI materials as possible, secondly in revising the discussion of markup theory and practice within the text to reflect current thinking. A few sections of the current text (the Gentle Introduction to SGML and the discussion of Extended Pointer syntax are two examples) will need substantial rewriting. For the most part, however, we think the Guidelines have stood the test of time well and can be recommended to a new generation of text encoders scarcely born at the time they were first formulated.

Lou Burnard and Steve De Rose (Editors)

Oxford and Providence, May 2001.

Up: Appendix C Prefatory Notes Previous: Appendix C1. Introductory Note (November 2001) Next: Appendix C3. Introductory Note (May 1999)