> I'm not sure if:
> a) the above DOCTYPE is specified properly, or
> b) the W3C validator is buggy, or
> c) the P5 DTD is buggy, or
> d) the 'type' attribute is not intended to be supported for <ref>
>    in P5.

I believe the answer is (c), the DTD is in error. The declaration for
%att.pointing.attributes; in tei.dtd (line 741) occurs *before* the
linking module is loaded (line 1948), and %att.pointing.attributes;
is defined as having type= (and evaluate=) in that module.

In DTD language, the first declaration wins, and subsequent
declarations are ignored. Thus since the null declaration on line 741
is in effect when the linking module is loaded, when the linking
module tries to declare %att.pointing.attributes; to include type=
and evaluate=, nothing happens.