- See TEIWiki:IdleTalk#Categories -- my guess is now that it was meant for DTD extensions as opposed to ODDs. Piotr 14:54, 26 September 2007 (BST)
From the Guidelines
Here's a different interpretation of the term:
(from http://tei.oucs.ox.ac.uk/P5/Guidelines-web/en/html/USE.html 22:30, 25 October 2007 (BST))
- A document is said to use a TEI Extension if it is a well-formed XML document which is valid against a TEI Schema which contains additional distinctions, representing concepts not present in the TEI abstract model, and therefore not documented in these Guidelines. Such a document cannot, in general, be algorithmically conformant since it cannot be automatically transformed without loss of information. However, since one of the goals of the TEI is to support extensions and modifications, it should not be assumed that no TEI document can include extensions: an extension which is expressed by means of the recommended mechanisms is also a TEI document provided that those parts of it which are not extensions are TEI conformant, or conformable.