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 the TEI technical standard, a journal, a wiki, a GitHub repository and a toolchain. TEI guidelines The TEI Guidelines collectively define a type of XML format, and 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 is primarily semantic rather than presentational; the semantics and interpretation of every tag and attribute are specified. There are some 500 different textual components and concepts (, , , , , etc.); each is grounded in one or more academic disciplines and examples are given. Technical details 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; to allow representation of characters that do not qualify for Unicode inclusion and 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. TEI Lite is an example of such a customization. It defines an XML-based file format for exchanging texts. It is a manageable selection from the extensive set of elements available in the full TEI Guidelines. As an XML-based format, TEI cannot directly deal with overlapping markup and non-hierarchical structures. A variety of options to represent this sort of data is suggested by the guidelines. Examples The text of the TEI guidelines is rich in examples. There is also a samples page on the TEI wiki, which gives examples of real-world projects that expose their underlying TEI. Prose tags TEI