Hi Sean:
Ive already made a fix in the 4.4.0 branch to preserve the global
attribute Conventions=CF.1-x if that exists in the source file. Easy to
do and its the right thing.
More difficult is to guarentee that all CF semantics get preserved in
the translation. The subsetting process has to change the coordinate
system, but we try to pass everything else through. Let us know any
issues and we will try to fix. We are looking at the ones that Seth has
reported.
The problem is that the damn software has to be told exactly what to do!
"Read the CF Conventions document", I said. Sheesh.
John
On 8/30/2013 1:59 AM, Gaffney, Sean P. wrote:
Hi John and all,
My initial reaction was the same as Seth's in that I felt
uncomfortable that any aspect of the metadata was being altered.
However, if it can be confirmed that only change occurring will be
the alteration of the Conventions attribute back to 1.0, that is
something we can handle with a declaration to the user.
As it stands, I've inspected the variables and attributes for the
model data we've got at present once they've been run through THREDDS
and so far, there are no actual changes apart from the convention
being altered from 1.4 on the data we received, back to 1.0 in the
output. My concern is whether this situation could be guaranteed into
the future, as we at BODC receive more complex oceanographic model
data in CF 1.6.
Cheers
Sean
-----Original Message----- From: CF-metadata
[mailto:[email protected]] On Behalf Of John Caron
Sent: 29 August 2013 00:19 Cc: [email protected] Subject: Re:
[CF-metadata] thredds changing CF conventions version
Hi John and all:
For sure its a good idea to preserve the CF Conventions attribute if
it exists. I will add that to our issue tracker.
Remember that THREDDS is a general purpose subsetter, not specific
to CF. So we deal with lots of source datasets (eg GRIB) that arent
CF. The point is that we convert whatever we have to CF.
Up to this point, as CF versions have evolved, there hasnt been any
difference in the way that we write out these files. So im interested
if Ive missed something and there is some actual change in the file
structure that we should be tracking from Sean's POV. Other than the
actual version number.
John
On 8/28/2013 11:11 AM, John Graybeal wrote:
It isn't just about feature presentation, right? On the assumption
that the latest version is always most current (so everyone will
use the latest version if they can), I use the version as a proxy
for how current/up-to-date/sophisticated the data provider is.
It also gives me a clue about which standard name table version
they might use, though that version info is often available
elsewhere.
If true, this may help explain why so few data providers seemed to
be using 1.6, anyway....
John
On Aug 28, 2013, at 08:56, John Caron <[email protected]>
wrote:
Hi Sean:
What feature of CF are you using that you need to preserve the
version?
John
"If you torture data long enough, it will confess." -- Economist
Ronald Coase
On 8/28/2013 3:28 AM, Gaffney, Sean P. wrote:
Hi, Here at the British Oceanographic Data Centre we use
THREDDS to deliver and subset our numerical model data that we
hold in CF netcdf format. I've just been made aware that during
the delivery and subsetting process, THREDDS seems to be
converting the CF files we hold from whatever CF convention
they have been supplied in, to CF 1.0. Is this something that
the rest of the community are aware of, and if so, do people
consider it to be of major importance that the files outputted
by thredds are in a different convention to the source files
thredds interrogates? Cheers Sean Gaffney BODC
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