[rfc-i] On backwards compatibility for v2

Heather Flanagan (RFC Series Editor) rse at rfc-editor.org
Mon Feb 10 13:52:49 PST 2014

On 2/10/14 1:39 PM, Ted Lemon wrote:
> 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.

Based on my experiences to date, I agree with Ted that significant
changes in tools tend to result in a certain amount of backwards
incompatibility, even when backwards compatibility is a design goal.
That said, several members of the design team settled on the following
principle on our last call (I did not do a consensus call on this
statement, so I won't say the entire design team agreed to this) :

We would rather encourage backward compatibility but not be constrained
by it.

My expectation is that v3 will introduce new and different things in
order to make using xml for the creation of RFCs easier.  There will be
a tool that allows for conversion from v2 vocabulary to v3 vocabulary.
It seems that people have different opinions as to whether having such a
tool means that we are supporting backwards compatibility or not.


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