There appear to be differences between parsers as to
how they handle exceptions thrown by callback methods
in the ContentHandler (specifically, SAXException
exceptions). Some parsers notify these to the
registered ErrorHandler, others do not.
This makes it difficult for an application to ensure
that every error message is output exactly once.
(Specifically, Crimson does not notify such errors, and
I think most other parsers do).
It would be useful if the spec made it clear which is
the correct behavior. My own view is that it is better
if such errors are notified to the ErrorHandler.