Re: What to do given both SYSTEM and PUBLIC?

At 11:08 AM -0500 2/19/97, Steven J. DeRose wrote:
>At 12:52 PM 02/18/97 -0800, Joe English wrote:
>>Try to resolve either one.  If that fails, try the other.
>>It doesn't matter which one you try first.

>So two systems that do opposite things are both conforming? That seems very
>ODA-like (I take that as a negative): "your system can do either the logical
>structure, or the layout, or both" -- so immediately you end up with
>non-interoperable yet conforming systems. We should at *least* do what SGML
>Open did and requir systems to support both and give a way to configure the
>choice, even if we can't come to a single decision.

>>> * what to do if you are given both and the resulting files are different
>>This means that somebody somewhere has made a mistake.
>>We don't need to specify error recovery in this case.
>I'll buy that; but you'll likely never *discover* the error, since if you
>successfully resolve one ID it is unlikely you'll bother with the other.

    It means that authors who intend to use both SYSTEM and PUBLIC are
duty-bound to either use (and test) a programmatic solution that ensures
they are identical, or must test the document with both public-preferred
and SYSTEM-preferred resolution in place.

   In other words, it's like broken link testing -- a pain, but one that
enables  sensible implementation strategies... So yes, author error may
cause conforming implementations to do different things. This is no worse
than the C statement
j = j++ + j++; which can return a variety of values and have a variety of
side-effects on conforming C compilers.

    In this case, since the author has control, it's probably better to
just do _something_ instead of worrying about doing the _right thing_.

  -- David

David Durand              dgd@cs.bu.edu  \  david@dynamicDiagrams.com
Boston University Computer Science        \  Sr. Analyst
http://www.cs.bu.edu/students/grads/dgd/   \  Dynamic Diagrams
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