Ken MacLeod <ken@[...].us>  writes:
>    *For interoperability*, the empty-element tag must be used, and
>    can only be used, for elements which are declared EMPTY.
>  
>  This reads to me that if you are validating (not Expat), and the
>  parser comes across a start-tag and end-tag pair for an element that
>  is declared EMPTY or an empty-element for an element that is not
>  declared EMPTY, then it should be reported as a warning.

No. "for interoperability" has a well defined meaning:

   for interoperability
          A non-binding recommendation included to increase the chances
          that XML documents can be processed by the existing installed
          base of SGML processors which predate the WebSGML Adaptations
          Annex to ISO 8879.

So if you want to process your documents with xml tools or up to date
sgml tools, there is absolutely no difference between <some_tag/>  and
<some_tag> </some_tag>.

An xml tool that makes a distiction on how it processes the two cases
should be regarded as not conforming to the recommendation.

Yours, Florian.