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This is at the top of the frequently asked questions I get about XML.
The fact that nobody has come up with a simple and elegant solution
leads me to believe that there isn't one, as does the fact that nobody
has solved this in non-XML fields (database schemas, APIs, operating
systems, etc.) either.
Ian Graham wrote:
> My own experience, on a large enterprise Web services project, is that
> elegant schema / WSDL evolution is not possible. There is simply no way
> to constrain the schema changes such that all existing applications are
> guaranteed to work with the new versions. So we will create new services
> (and keep the old) if anything needs to change. We hope that governance
> will help limit/control this revving process.
> The situation is likely similar for other environments -- if you want to
> guarantee that all previous apps dependent on the schema work, then you
> can't change it.
> If you think a schema change is idiot proof, you likely just haven't
> found a suitably qualified idiot :-(