Trust and control (as Re: [xml-dev] Here's how to process XML documentsw

["Simon St.Laurent" <simonstl@simonstl.com>]

Somewhere along the line programmers learned that only completely 
perfect messages should be accepted.  In the early days this could be 
explained by lack of resources for handling variation, but somehow it 
developed into a deep brittleness in computing culture and infects our 
tools as well.

It's less a question of trust than a question of control, an insistence 
that every contract be met precisely for fear that we will be paralyzed 
if something is out of step.

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.

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

Thanks,
Simon

On 1/31/13 5:41 AM, Costello, Roger L. wrote:
> Michael Kay wrote:
>
> Tony prefaced his advice with "if you can't trust...". You (Roger)
> left that bit out.
>
> Perhaps you did this on the basis that you should never trust
> anything. But if you don't trust anything, why are you processing the
> XML at all?
>
> That is a fascinating and puzzling set of statements Michael.
>
> Yes, I never trust any external input. (That is, I design my
> applications and web services such that external input is not
> trusted.) I rigorously scrutinize external input prior to allowing it
> into my application or web service:
>
> I validate the input against a tightly constrained XML Schema and
> Schematron schema.
>
> This helps to ensure that the data ingested by my applications and
> web services receive is the data they expect to ingest.
>
> Based on the recent discussions I am thinking that it may be wise to
> also add normalization to the external input scrutinizer.
>
> Why would an application or web service be designed to trust external
> input? Perhaps there are circumstances where external input can be
> trusted, but surely they are extremely rare?


-- 
Simon St.Laurent
http://simonstl.com/