linkend attr required in =?UTF-8?Q?=3Cbiblioref=3E=3F?=

[maxwell <maxwell@umiacs.umd.edu>]

The DocBook 5 RNG schema
(http://www.docbook.org/xml/5.0b1/rng/docbook.rng) makes the 'linkend' attr
in the <biblioref> element obligatory.  But afaict, the documentation for
DocBook 5 does not require that attr on this element.  

Specifically, http://www.docbook.org/tdg5/en/html/biblioref.html does not
show the 'linkend' attr among the attributes specific to <biblioref>.  The
'linkend' attr apparently comes as one of the "common linking attributes." 
But there's no indication at the description of Common Linking Attributes
(http://www.docbook.org/tdg5/en/html/ref-elements.html#common.linking.attributes)
that this attribute should be obligatory, either.

In docbook.rng, on the other hand, the 'linkend' attr is one of two
possible attrs under db.common.req.linking.attributes, where the 'req'
presumably means 'required'.  And this db.common.req.linking.attributes is
among the attributes on the list db.biblioref.attlist, but it isn't
bracketed by <optional>...</optional>.  

So if the documentation is correct, then it seems like either
'db.common.req.linking.attributes' should be bracketed by
<optional>...</optional> under the def for the <biblioref> element
(although it seems odd to have a 'required' element be 'optional'), or more
likely the <biblioref> element should include the list
'db.common.linking.attributes', rather than the list
'db.common.req.linking.attributes'.

Or am I missing something?  Stepping back to the purpose of the
<biblioref> element, my midunderstanding is that one place this element is
used is inside a <citation>, so that you can add e.g. page numbers to a
citation.  And this is exactly what we want to do, e.g. we would like to
get the output
   Chomsky 1965:23-25
from something like
   <citation> Chomsky1965 <biblioref begin="23" end="25"/></citation>
(where 'Chomsky1965' corresponds to the <abbrev> element in one of our
<biblioref>s, or some such).  Given this XML frag, there's no need for a
'linkend' attr on the <biblioref>.

But maybe there is an issue of mixed content?  Perhaps this XML frag is
supposed to be
   <citation><biblioref linkend="Chomsky1965" begin="23"
end="25"/></citation>
?  If so, I guess the documentation should be clarified to say that the
'linkend' attr is obligatory on <biblioref> (and an example added to show
how to use <biblioref>: there is no example at present).

In sum, there seems to be a problem with either the documentation or the
schema--or me.  (Nah, can't be me...)

   Mike Maxwell