The description of dataRef/@key is "the identifier used for this
datatype specification". This is confusing, if not outright nuts: the
identifier used for this particular data reference element would be
specified on @xml:id.
I'm of a mind that the three "what I'm referring to" attributes
should have parallel descriptions. Something like:
key = The datatype being referred to from the set of provided or
custom TEI datatypes, indicated by its identifier (e.g.,
"teidata.language")
name = The datatype being referred to from the datatypes found
in _XML Schemas: Part 2: Datatypes_, indicated by its
name (e.g., "gYear")
ref = The datatype being referred to in an external datatype
library, indicated by a URI
although I'm sure those can be improved upon.
Meanwhile I've discovered that the
dataRef.xml/elementSpec/listRef/ptr/@target pointed to the wrong
section, and that in that file @ref was defined as a name, not a URI.
I have fixed these corrigible errors, but did not want to muck with
the wording on my own.