[rfc-i] On backwards compatibility for v2

Ted Lemon mellon at fugue.com
Mon Feb 10 13:39:34 PST 2014


On Feb 10, 2014, at 4:32 PM, Dave Crocker <dhc at dcrocker.net> wrote:
> Having an up-front declaration that backward compatibility is a requirement -- that v2 docs can be directly processed by a v3 engine -- imposes a useful discipline on the way people thing about enhancements.

IOW we should definitely argue about this now, rather than later.

Sigh.

There's (one assumes) a reason why we chose to use a really standard representation like XML in XML2RFC.   That reason would be that there are lots of tools for doing transformations on XML.

I suspect that the meat of your argument is that if the v3 format isn't backward compatible to v2, the tool won't necessarily work with all v2 documents.   But the move from v1 to v2 has already shown us that the even when the format isn't changing in major ways, different tools may interpret it differently, and bugs may arise.

This isn't something that can realistically be prevented without a lot more developmental rigor than I anticipate.   So although I hear what you are saying and agree that it makes sense in theory, I don't think it makes sense in practice.   

Whether we intend for v2 to be incompatible with v3 or not, it will be.   And we will have to deal with that.   So we are really just picking between two different types of incompatibility, and I see no compelling argument we have to have right now to determine which of those we should choose.   Let's cross that bridge when we come to it.



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