it seems to me that we could solve this by making <idno> (and many other things?) a member of att.declarable (http://www.tei-c.org/release/doc/tei-p5-doc/en/html/ref-att.declaring.html) which immediately allows association with eg a taxonomy. I would argue that saying <idno type="doi"> is not _intended_ to be used by the type
of downstream processor which John or I write; it is in that class of classification and discrimination which the project makes up for its own purposes.
I suspect that generic TEI stylesheets can safely ignore @type at almost all times - exceptions are <list> and <divGen>. If I am right, then I am almost tempted to say that <list> needs a different attribute to distinguish ordered, unordered and gloss, because this is such a common, and important, bit of information.
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