To create a formal taxonomy of concepts:
<teiHeader> <!-- ... --> <classDecl> <taxonomy> <category xml:id="G.drama"> <catDesc>drama</catDesc> <category xml:id="G.drama.mixed"><catDesc>mixed</catDesc></category> <category xml:id="G.drama.prose"><catDesc>prose</catDesc></category> <category xml:id="G.drama.verse"><catDesc>verse</catDesc></category> </category> <category xml:id="G.fiction"> <catDesc>fiction</catDesc> <category xml:id="G.fiction.letter"><catDesc>letter</catDesc></category> <category xml:id="G.fiction.novel"><catDesc>novel</catDesc></category> <category xml:id="G.fiction.other"><catDesc>other</catDesc></category> <category xml:id="G.fiction.story"><catDesc>story</catDesc></category> </category> <category xml:id="G.non-fiction"> <catDesc>non-fiction</catDesc> <category xml:id="G.non-fiction.essay"><catDesc>essay</catDesc></category> <category xml:id="G.non-fiction.letter"><catDesc>letter</catDesc></category> <category xml:id="G.non-fiction.other"><catDesc>other</catDesc></category> </category> <category xml:id="G.verse"> <catDesc>verse</catDesc> <category xml:id="G.verse.lyric"><catDesc>lyric</catDesc></category> <category xml:id="G.verse.narrative"><catDesc>narrative</catDesc></category> <category xml:id="G.verse.other"><catDesc>other</catDesc></category> </category> </taxonomy> </classDecl> <!-- ... --> </teiHeader>