A posting from Lou Burnard invites comment on the publication of updated XML DTDs for the Text Encoding Initiative Guidelines. Based upon extensive public review, the XML DTDs have been improved and corresponding revised documentation has been created in HTML and PDF format for the TEI Guidelines. Approval of the new P4 edition by TEI Technical Council and final publication is expected within the near future. Already widely adopted for use in digital library projects, the TEI Guidelines are "intended for use in interchange between individuals and research groups using different programs and computer systems over a broad range of applications... The Guidelines apply to texts in any natural language, of any date, in any literary genre or text type, without restriction on form or content. They treat both continuous materials ('running text') and discontinuous materials such as dictionaries and linguistic corpora. The primary goal of the P4 revision has been to make available a new and corrected version of the TEI Guidelines which: (1) is expressed in XML and conforms to a TEI-conformant XML DTD; (2) generates a set of DTD fragments that can be combined together to form either SGML or XML document type definitions; (3) corrects blatant errors, typographical mishaps, and other egregious editorial oversights; (4) can be processed and maintained using readily available XML tools instead of the special-purpose ad hoc software originally used for TEI P3. A second major design goal of this 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."

Part of the P4 XML Version of the TEI Guidelines includes an update to the widely-referenced TEI 'Gentle Introduction', now titled "A Gentle Introduction to XML." This chapter serves as an excellent introduction to XML for "document-based" applications. From the introduction: "The encoding scheme defined by these Guidelines may be formulated either as an application of the ISO Standard Generalized Markup Language (SGML) or of the more recently developed W3C Extensible Markup Language (XML). Both SGML and XML are widely-used for the definition of device-independent, system-independent methods of storing and processing texts in electronic form; XML being in fact a simplification or derivation of SGML. In the present chapter we introduce informally the basic concepts underlying such markup languages and attempt to explain to the reader encountering them for the first time how they are actually used in the TEI scheme. Except where the two are explicitly distinguished, references to XML in what follows may be understood to apply equally well to the TEI usage of SGML. For a more technical account of TEI practice see chapter 28 on 'Conformance'; for a more technical description of the subset of SGML used by the TEI encoding scheme, see chapter 39 on 'Formal Grammar for the TEI-Interchange-Format Subset of SGML'... XML is an extensible markup language, used for the description of marked-up electronic text. More exactly, XML is a metalanguage, that is, a means of formally describing a language, in this case, a markup language..."