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.