I don't think there's any pressing need to do this, but it has its attractions. If we do work on an incompatibly different file format, it should be a long-term project to produce a format to serve for the next 30 years, not a hasty process that we'd need to redo.
Agreed. And I don't think we should be sacrificing clean design for any kind of compatibility.
I had been thinking about a PNG-like "chunk" structure which would allow implementations to ignore anything they don't understand. I thought about proposing this back when we were talking about tz-to-metazone mapping (something which I still think should belong to this project rather than CLDR). That would take care of future extensibility.
What's wrong with XML. Parsers are easy to obtain. The code that interprets the structure can ignore any entity they don't understand, giving complete extensibility. Or you can have a specific entity: <mandatory type="abc"> ... </mandatory> which means "if you don't know what an 'abc' is, raise an error now rather than trying to understand the contents". -- Clive D.W. Feather | If you lie to the compiler, Email: clive@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646