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 [[email protected]]
Sent: 05 August 2011 16:30
To: Lowry, Roy K.; [email protected]
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: [email protected]<mailto:[email protected]>
[[email protected]<mailto:[email protected]>] On
Behalf Of Nan Galbraith [[email protected]<mailto:[email protected]>]
Sent: 04 August 2011 19:17
To: Steve Hankin; [email protected]<mailto:[email protected]>
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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