[CF-metadata] "positive" attribute

[Roy Lowry]

Hi Bryan,

I would prefer any changes in Standard Names conventions/practices to be by revolution rather than evolution, even if that evolution is from bad to good practice. Semantic modelling and ontology creation are much easier if there are consistent patterns in the base lists. So, I agree with Jonathan even if my reasons are somewhat different.

Cheers, Roy.

>>> Bryan Lawrence <b.n.lawrence at rl.ac.uk> 6/28/2007 4:30 pm >>>

> data would not be self- describing. Not knowing the sign convention is a
> serious problem for analysis of data. The fact that the data would not be
> CF-compliant would be no consolation for its being useless. It is better to
> prevent problems happening.

(Possible response: Make the sign mandatory. I think asking someone who didn't 
read the CF convention when they designed their model to rerun the model or 
rewrite the output is a bigger ask than adding one tiny attribute to each 
variable ... and one which which would make software deciding what to do with 
comparing data much easier to design).

> > What happens if I build (or have) a model which happens to have a
> > different sign convention than the one chosen thus far? Do I have to
> > reprocess all my data, or introduce a duplicate set of standard names
> > with the opposite convention embedded. The latter doesn't seem right!
>
> You have to introduce other standard names. We already have several upward/
> downward pairs for this reason, but it turns out that in practice there is
> not lot of such duplication, because people tend to use common conventions,
> so it's never been suggested to present a significant problem. Hence I
> think the evidence is that this pragmatic decision was reasonable, and
> although other decisions could have been taken there is at present no
> reason to change the guidelines.

That's an argument for inertia, which is certainly pragmatic, but I think 
there are things coming for which this is not going to be so easy. What about 
family chemistry? I bet there is no convention on the deltas between 
families? What about different soil/ice/river/hydrology models? I know one of 
our guiding principles is not to worry about the future too much, but a 
little thought for *very* little overhead would help significantly in the 
future. I think Forrest's first email was on the button, our primary 
assumption is that things have a default (up/down) orientation will be much 
harder to sustain in the muddy world (pun intended) of earth system models, 
and having two standard names is just more work than is necessary ...

What I'm suggesting is that the guidelines for new "groups" of standard names 
could be different from those in the past. I'm also suggesting something that 
will make the business of *maintaining* lists (and soon, ontologies, easier).

But having said all this, I dont feel so strongly about it that I intend to 
say any more on this, unless someone else feels strongly enough to force a 
vote ... :-)

Cheers
Bryan
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