This customization, called "DTABf" for short, is usually called "DTA 'Base Format'" in English. It is a strict subset of TEI P5 designed for encoding structural features in written corpora, especially historical ones. It is recommended as the format for written corpora for CLARIN-D and by the German Research Foundation (DFG).
An introduction in English is available at http://www.deutschestextarchiv.de/doku/basisformat_en , and documentation, ODD, and RNG schemas are at http://www.deutschestextarchiv.de/doku/basisformat/schema.html (in German).
For background, see an article in jTEI.