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Re: [xml-dev] Trust and control (as Re: [xml-dev] Here's how toprocess XML documents written in German)

On Thu, 2013-01-31 at 07:16 -0500, Simon St.Laurent wrote:
> Somewhere along the line programmers learned that only completely 
> perfect messages should be accepted.

The difficulty has always been two-fold.

First, that you have to allow for every variation in the software, as
you don't want software to crash or allow execution of arbitrary code
accidentally (vulnerabilities). It's interesting to note that the
widespread adoption of Intel's 808x little-endian architecture greatly
increased vulnerability to stack attacks.

Second, that error correction is difficult.

Error correction that varies from program to program means
interoperability is limited to the subset of data that gets treated the
same way everywhere. This is what, for example, HTML 5 is about (partly)
- documenting that subset for Web browsers, and trying to broaden it by
having the browsers all use the same parsing and error correction
techniques for new content. 


> I could see the value of well-formedness, though I question even that 
> lately.  I don't understand, though, why we regularly insist that the 
> only information worth processing is that which arrived in pristine 
> condition.

That's a stronger statement than I'd make.

If I make a mistake in a program, the chances are that
(1) the compiler or interpreter catches it
(2) I catch it in my unit tests
(3) It's caught in application tests and Q/A
(4) A customer complains
(5) Everything seems fine until the 'plane tries to land when
    the wind-speed is less than the ambient air temperature and
    the 'plane is full of fuel.

The cost of fixing problems increases at each stage.

I've used a C compiler that could correct a large class of input errors;
it detected when it had done so and did not generate code, but gave more
helpful error messages.

> Programmers of the world, throw away your schemas!  You have nothing to 
> lose but your existing toolset! (aka your chains...)

But I _like_ chains.


Liam Quin - XML Activity Lead, W3C, http://www.w3.org/People/Quin/
Pictures from old books: http://fromoldbooks.org/
Ankh: irc.sorcery.net irc.gnome.org freenode/#xml

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