Elliotte Harold wrote:
Certainly SQL databases can be evolved, but it's really hard to do.
I've never had a problem with it 10 years ago when we changed and evolved our business processes to constantly improve a part management and ordering system.
It was always a simple matter - you either integrated with the existing environment, or you extended the environment, or both.
If we had a complete database change for a new set of functions, you scheduled a day to export all the data and reimport in the new format. No big deal.
Now, you might say "well, with XML you don't have to export and reimport data" - for which I would say I don't believe that is the case in a /practical/ sense.
Sure, the application may be designed to not care about the data format, but when you have to start relating one set of records with another set of records, you will start using keys. And when you decide that you want to completely break up data in one field into 2 fields because of some oddity, your going to have to take all existing data and fix it.
I just don't see the discussion as a relational database vs XML database debate. It seems to be an debate on how IT groups in business are structured. Give it 10 years and the "XML scheme administrators" will be just as inflexible to change and causing problems - and someone will be promoting some new method of storing data as an answer to a business process problem.
I'm not saying don't use XML databases and files, I think they are good answers for a whole mess of applications.
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