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  • From: Kurt Cagle <kurt.cagle@g...>
  • To: Michael Kay <mike@s...>
  • Date: Tue, 12 Nov 2013 21:41:23 -0800

The biggest problem with constraints that I've seen has to do with the fact that data itself, in the real world, has this very annoying tendency to morph over time. That's in great part because programmers do not think in terms of resources that evolve but data structures that represent state that is most useful to them, something that strong typing in particular has reinforced. XML was a radical departure from that model - unlike databases, where type was intrinsic, atomic, and implicit to the implementation, and binary objects, which similarly placed constraints upon type for optimization, XML was extrinsically typed, in an advisory rather than compulsory fashion. 

I think this is a lesson lost on many corporate developers who see XML only as an intermediation format from one strongly typed object to another (I've often wondered whether so much of the bad press that XML gained would have been spared if JSON had come out a few years earlier, and whether it would be JSON that would be villified as being too unwieldy as an object broker language, when the real culprit was the tendency for application developers to put too much of the business logic of an application, rather than more generic system logic, into heavyweight OOP in the first place).  

Kurt Cagle
Invited Expert, XForms Working Group, W3C
Managing Editor, XMLToday.org
443-837-8725



On Tue, Nov 12, 2013 at 9:16 PM, Kurt Cagle <kurt.cagle@g...> wrote:
+1

On Mon, Nov 11, 2013 at 4:38 PM, Michael Kay <mike@s...> wrote:
n a perfect world, we wouldn't put such constraints in our systems. However, I don't think that systems that have such constraints are "deeply broken". On the contrary, I think all human attempts to monitor, regulate, and systematize the world we live in rely on putting things into categories and labelling the categories as if they were unambiguous. Constraints saying that every company has two or more directors are typically imposed by legislators rather than IT people, and it's often IT people who have to cope with the fact that the constraints are broken (does the company cease to exist if the directors are killed in a plane crash?). We simply don't have the ability to design systems without such constraints, and a constraint language that enables us to be explicit about the constraints the system is imposing makes the system less broken than it would be if the constraints were there but not clearly articulated.



Kurt Cagle
Invited Expert, XForms Working Group, W3C
Managing Editor, XMLToday.org




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