The Text Encoding Initiative is an international committee supported by a wide range of scholarly societies, which is developing guidelines for the encoding of texts for a range of scholarly and commercial purposes. The TEI is a joint European/American project involving scholars all over the world. While not yet near completion, it has already committed to the use of SGML as a basic text description language. TEI guidelines are expected to include standard tags for units commonly of interest, and explicit Document Type Definitions for various kinds of standard documents, as well as definitions of how to extend the guidelines when new content objects need labels.
(DeRose et al. 1990, 11)