When to Validate XML?

Anyone interested in sharing their thoughts on under what circumstances you should validate XML? 

I think this board has really had some good discussions lately (i.e. Database Decision Tree, Determining ID-ness in XML) and this is one issue that still seems to draw the most debate in the inner-circles of my company.

Some folks feel that validation should ALWAYS be done regardless of the circumstance (a bit radical it may seem). Others feel that XML validation is simply a waste of time.  Some groups feel that schemas are not advanced yet to do validation very intelligently (i.e. problems validating date formats), and that the applications are still the best choice to validate your data.  People involved with integration feel that if the publisher and the subscriber applications/databases BOTH do validation that XML validation is an extreme misuse of resources.  And on and on….

With out nit-picking the examples I just laid out on the table can we share some general thoughts on When to Validate and When Not to Validate XML?

Who knows, if this is a successful conversation perhaps we can give Leigh Dodds enough ammo for next week’s article.  J

Brian Magick