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At 9:00 AM -0400 4/16/04, Stephen D. Williams wrote:
>Binary doesn't imply there isn't any well-formedness checking, obviously.
For once I agree. Obviously, binary doesn't imply that. However, in
practice, the binary formats I do see rarely do as much
well-formedness checking as a parser does, either in the XML domain
or elsewhere. Speed gains that come from eliminating well-formedness
checking should not be attributed to a binary format. Similar gains
can be had by eliminating well-formedness checking when processing
real XML (Not that I recommend doing that of course).
>Incremental, or lazy evaluation, well-formedness is useful and
>potentially protects applications just as well as full
>well-formedness with better efficiency.
Simply not true. It doesn't come close to protecting applications as
well as full checking.
>Allowing the application the option of avoiding repetitive or
>unncessary well-formedness checking is a valid strategy. Your
>argument that data that a 'program' receives must always be fully
>validated in any situation could just as easily be extended to
>libraries and modules receiving DOM references or similar. What one
>system may do with libraries or software modules, another may do
>with plugins and another may do with n-tier processing steps. Does
>the granularity of the implementation somehow necessarily change the
>fundamental likelihood of corruption?
All published interfaces should verify their preconditions. Libraries
should (and indeed the ones I write do) verify that input passed to
them from outside the library is correct. For instance, if I publish
an interface that expects a DOM object that can be serialized as
namespace well-formed XML, and you pass me a DOM object that can't
be, then the precondition is violated. The method should detect this
and throw an exception. And indeed this is exactly what I do:
http://www.cafeconleche.org/XOM/apidocs/nu/xom/converters/DOMConverter.html#convert(org.w3c.dom.Document)
Cowboy coding like you suggest scares me. I certainly wouldn't want
to have to trust any software written to such standards. Regrettably
I know there's a lot of such software out there, which is more reason
than ever for my software to be very careful about what it receives
from your software.
--
Elliotte Rusty Harold
elharo@metalab.unc.edu
Effective XML (Addison-Wesley, 2003)
http://www.cafeconleche.org/books/effectivexml
http://www.amazon.com/exec/obidos/ISBN%3D0321150406/ref%3Dnosim/cafeaulaitA
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