Text Encoding Initiative

The Text Encoding Initiative (TEI) is a text-centric community of practice in the academic field of digital humanities, operating continuously since the 1980s. The community currently runs a mailing list, meetings and conference series, and maintains an eponymous technical standard, a journal, a , a SourceForge repository and a toolchain.

The TEI Guidelines, which collectively define an XML format, are the defining output of the community of practice. The format differs from other well-known open formats for text (such as HTML and OpenDocument) in that it's primarily semantic rather than presentational; the semantics and interpretation of every tag and attribute are specified. Some 500 different textual components and concepts (word,sentence,character,glyph,person, etc.); each is grounded in one or more academic discipline and examples are given.

The standard is split into two parts, a discursive textual description with extended examples and discussion and set of tag-by-tag definitions. Schemata in most of the modern formats (DTD, RELAX NG and W3C Schema) are generated automatically from the tag-by-tag definitions. A number of tools support the production of the guidelines and the application of the guidelines to specific projects.

A number of special tags are used to circumvent restrictions imposed by the underlying Unicode; glyph to allow representation of characters that don't qualify for Unicode inclusion and choice to allow overcome the required strict linearity.

Most users of the format do not use the complete range of tags but produce a customisation, using a project-specific subset of the tags and attributes defined by the Guidelines. The TEI defines a sophisticated customization mechanism known as ODD for this purpose. In addition to documenting and describing each TEI tag, an ODD specification specifies its content model and other usage constraints, which may be expressed using schematron.

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