Hi Nan,
At the risk of being shot for herecy, I maintain the belief that in the current technological environonment packing everything inside the straightjacket container of a physical file is an anachronism. As you've probably guessed my view is that metadata and its associated semantics have data structures that incorporate complex interrelationships, which can only be properly encoded in formats like XML. So, I would have an attribute in the CF file holding a permanent identifier that is guaranteed to be resolvable from now until eternity into an XML file delivering usage metadata.
Cheers, Roy.
________________________________
From: Nan Galbraith [ngalbraith at whoi.edu]
Sent: 05 August 2011 16:30
To: Lowry, Roy K.; cf-metadata at cgd.ucar.edu
Subject: Re: [CF-metadata] per-variable metadata?
Hi Roy and all -
Do you see a possible place for this metadata in a more
structured attribute system, or somewhere else in the NetCDF
file structure? Or are you thinking that we need metadata
outside our CF files?
Since CF has the precedent of putting other quality-related
information (flag values, uncertainty, etc.) in ancillary variables,
it seems (or seemed) reasonable to me to include more complete
provenance info there. It might blur the line between data and
metadata, but I don't see another solution without higher costs,
at the moment.
I'm looking forward to someone solving this, and I'm glad to
hear that SeadataNet may be looking at it.
Cheers -
Nan
On Aug/04/2011 4:13 PM, Lowry, Roy K. wrote:
Hi Nan,
Encoding what I would regard as usage metadata into ancilliary variables is one solution, but I would much rather see a formalised metadata model for doing this. As you say a standard way of doing this is long overdue. My hope is that SeadataNet II starting later this year will take on and address this challenge. However, if anybody knows of anything already in existence that fits the bill it would be good to prevent yet another wheel being reinvented.
Cheers, Roy.
________________________________
From: cf-metadata-bounces at cgd.ucar.edu<mailto:cf-metadata-bounces at cgd.ucar.edu> [cf-metadata-bounces at cgd.ucar.edu<mailto:cf-metadata-bounces at cgd.ucar.edu>] On Behalf Of Nan Galbraith [ngalbraith at whoi.edu<mailto:ngalbraith at whoi.edu>]
Sent: 04 August 2011 19:17
To: Steve Hankin; cf-metadata at cgd.ucar.edu<mailto:cf-metadata at cgd.ucar.edu>
Cc: Jeff deLaBeaujardiere
Subject: Re: [CF-metadata] per-variable metadata?
Hi Steve -
I'm very interested in the background discussion on this -
any chance of bringing it into the foreground?
I'm using ancillary variables in 2-D in situ data files to describe
instruments and things like precision, accuracy, sample scheme,
etc.. For temperature files from moorings where different sensor
types are at different depths, I'd like to use something like
TEMP:ancillary_variables = "Instrument_manufacturer Instrument_model
Instrument_sample_scheme Instrument_serial_number TEMP_qc_procedure
TEMP_accuracy TEMP_precision TEMP_resolution";
and then
short INST_SN(depth) ;
INST_SN:long_name = "instrument_serial_number" ;
... etc., etc.
If there's going to be a standard way to do this, I'd really like to
know about it - sooner rather than than later.
Thanks -
Nan
On 8/4/11 11:35 AM, Steve Hankin wrote:
Hi Jeff,
Each variable in a CF file may possess an |ancillary_variables| attribute, that points to variables that have relationships (
http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.5/cf-conventions.html#ancillary-data). To attach flags to a variable, use |ancillary_variables| to point to a variable that has |flag_values||| and |flag_meanings |attributes (
http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.5/cf-conventions.html#flags).
We have started a discussion in the background, whether an example that illustrates this should be included in the CF documentation.
- Steve
=====================================================
On 7/14/2010 6:21 AM, Jeff deLaBeaujardiere wrote:
In another discussion, Steve Hankin wrote:
> CF generally favors attributes attached to variables over attributes attached to files
This reminds me of a question I wanted to ask: does CF have any conventions regarding how to handle data that contains multiple observed quantities with different quality flags, comment fields or other attributes for each quantity?
-Jeff DLB
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