It does seem that CF and ACDD don't overlap and can complement
each other; we're moving towards using both in the oceansites project.
The problem is that there does not seem to be any public discussion of
how these work together, or who will make sure they continue to work
together without collisions. Is it really never going to be an issue?
ACDD may only intend to provide guidance, but it seems it's being adopted
fairly widely as a standard. Its main drawback is that it has no public
forum,
like the CF list, to help users implement it or to get feedback on
problems.
I've asked several questions about the ACDD over the past 3 years, using
the email link on the web page, but have never gotten a reply.
One example - the hard wired role of "creator" is too vague for in situ
data;
is it the PI who collected the data? Someone who changed a single attribute
in a file? Guidance on the keywords is sparse, and this is listed as
being in
development - which, I would hope, would involve some public discussion.
- Nan
Kenneth Casey wrote:
Craig - to be absolutely clear: the ACDD attributes in no way
conflict with CF. They just provide some recommendations on what
names to use for some attributes. Using a common set of attribute
names enables us to build tools around those attributes that work
well across different data sets. Within NOAA for example there is a
project called the Unified Access Framework that has linked together
dozens of disparate THREDDS Data Servers through a single THREDDS
catalog. The larger number of data sets in that catalog that use the
ACDD the easier it is to build and maintain a dynamic crawler to
update that catalog on a regular interval. Also, it becomes possible
to extract automatically ISO "discovery level" metadata and feed it
into standard search mechanisms thereby making it possible to find
what you want amidst that sea of information. Other groups have built
tools to automatically crawl these attributes to assess the data in
terms of it's metadata robustness. That knowledge is useful for a
variety of purposes.
I will be interested to hear what folks on this list have to say
about CF "taking up" the ACDD recommendations. That might be fine but
I am not sure it is necessary. ACDD is focused purely on improving
discovery. CF focuses on other things like usability and
understanding, at least as far as I understand it.
Ken
--
On Jul 10, 2010, at 5:38 AM, Craig Donlon <[email protected]
<mailto:[email protected]>> wrote:
Dear all:
CF is quite light on global metadata and metadata suitable for data
discovery and interoperability. Within the Group for High
Resolution Sea Surface Temperature (GHRSST, see
http://www.ghrsst.org) we are updating our product technical
specifications (GDS) documentation. We want to provide more
flexibility and interoperability with our products in a 'future
proof' manner. GHRSST is handling 25Gb data per day in an
international context with many thousands of files in NRT.
Our latest specs. have included the NetCDF Attribute Convention for
Dataset Discovery
(ACDD http://www.unidata.ucar.edu/software/netcdf-java/formats/DataDiscoveryAttConvention.html)
and this has raised some questions about our CF compliance. I
realise that CF allows extensions, but what I am asking for is some
guidance on the future aspirations of CF for discovery metadata. I
like the ACDD recommendations and Ideally, I would like to be able
to write in our GHRSST data products that we are fully CF compliant.
Does the CF community anticipate taking up the
ACDD recommendations in the near future? What
are peoples thoughts on CF and improved metadata discovery?
I look forward to your comments and advice,
Best regards
Craig Donlon (Chair of the GHRSST International Science Team)
--
*******************************************************
* Nan Galbraith (508) 289-2444 *
* Upper Ocean Processes Group Mail Stop 29 *
* Woods Hole Oceanographic Institution *
* Woods Hole, MA 02543 *
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