Under-specification for @refcol?

Do we say that it isn't used?  Not used by whom?  How do we know?

Do we say that its use is not defined or is implementation specific?

Do we say, as Eliot suggested, that it is "reserved for future use"?

Do we say that the attribute is obsolete and its use is deprecated?

One or the other of the last two choices seem better to me.

-Jeff

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