[CF-metadata] CF-2.0 Convention discussion

From: Jonathan Gregory <j.m.gregory>
Date: Fri, 19 Sep 2014 15:11:41 +0100

Dear John

> So I propose we have a 3 month discussion period where we clarify what the
> issues are and possible improvements or changes. We wont try too hard
> during that period to create final wording, and divergences of opinion will
> be recorded rather than resolved. After that we will have another 3 month
> period where we try to write a document and make decisions.

It is good to have a timescale for discussion. That might not be long enough,
but let's see!

> I propose these ground-rules for what we discuss:
> 1. Changes needed to use the extended model.
> 2. Possible things to deprecate or remove.
> 3. Possible new functionality esp if it comes from using the extended
> model.
> 4. Backwards compatibility is desirable, but not required if there is a
> substantial advantage in simplicity and clarity. So respect precedent and
> dont constrain important innovation.

By "extended model" do you mean the netCDF4 model? I don't think we should
begin with an *aim* to use the netCDF4 model. The question is, what do we need
to do which we *can't* do in the classic model, or could be done much more
easily in the extended model than in the classic model? That is, changes to CF
should be driven by use-cases, not technology. So I would combine 3 and 1 as

(1) What use-cases cannot be met with the classic model, or could be met much
more easily with the extended model?

Since "remove" implies "backward-incompatible", I would put (2) as

(2) Possible things to deprecate (because there is a better way to do it
- I assume - are there other reasons?)

Then

(3) Possible things to remove, or to require if they are currently only
optional. Such changes mean backwards-incompatibility. I think that the
default should be backwards compatibility. There has to be a strong advantage
for making incompatible changes. (NB I am not saying that backward
incompatibility is out of the question!)

I do not think we should introduce a new way of doing something because
it might look nicer, unless it is clearly functionally much better than the
existing way. Also, if we introduce a new way to do something, we should
carefully consider removing the old way, because it is easier for users of
the convention if there is only one way to do something.

Whatever way the discussion is done, I think it's important that
- it should be public to read and contribute to
- it should have a history, so we can all see what we and others said earlier.

Best wishes and thanks

Jonathan
Received on Fri Sep 19 2014 - 08:11:41 BST