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Bob et al.,So I looked more closely at the references you supplied in your first email and I am left additional questions and confusion. I hope that one of the recipients of this message can shed some light on what appears to me to be a conflict in either the intent or the interpretation in the way that NetCDF and CF-1.4 define use the attribute Conventions.
In section 2.6.1 of the CF-1.4 conventions page "Identification of Conventions" ( http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.4/cf-conventions.html#identification-of-conventions ), it says this:
We recommend that netCDF files that follow these conventions indicate this by setting the NUG defined global attribute Conventions to the string value "CF-1.4" . The string is interpreted as a directory name relative to a directory that is a repository of documents describing sets of discipline-specific conventions. The conventions directory name is currently interpreted relative to the directory pub/netcdf/ Conventions/on the host machine ftp.unidata.ucar.edu. The web based versions of this document are linked from the netCDF Conventions web page.
But the NetCDF Conventions page ( http://www.unidata.ucar.edu/software/netcdf/conventions.html ) which is referenced at the end of that section clearly indicates that comma or space separated lists of conventions names as a value for the attribute Conventions is specifically allowed:
It is possible for a netCDF file to adhere to more than one set of conventions, even when there is no inheritance relationship among the conventions. In this case, the value of the `Conventions' attribute may be a single text string containing a list of the convention names separated by blank space (recommended) or commas (if a convention name contains blanks), for example
:Conventions = "XXX YYY" ;
So from my reading of this:
- The current use of the Conventions attribute at ERD is correct
according to the NetCDF Conventions page.
- Section 2.6.1 of the CF-1.4. convention does not specifically address the use of multiple space or comma separated values in the value of the Conventions attribute. However it does seem that the text of section 2.6.1 would indicate a very different specific meaning of the string value of the Conventions attribute (as a directory name in a file system) than that described in the NetCDF conventions document.
Is it really the intent of the authors of CF-1.4 that the meaning of the NetCDF Conventions attribute be overridden if the CF-1.4 convention is supported?
Is it the intent that the attribute Metadata_Conventions from the NetCDF Attribute Convention for Dataset Discovery (http://www.unidata.ucar.edu/software/netcdf-java/formats/DataDiscoveryAttConvention.html ) is to supersede the use of the netCDF Conventions attribute, thus freeing the Conventions attribute for use as a directory name?
And in the CF-1.4 section 2.6.1 this sentence: "The string is interpreted as a directory name relative to a directory that is a repository of documents describing sets of discipline-specific conventions." Indicates an entirely different meaning/interpretation/ semantics for the value of the Conventions attribute that is in direct conflict with the one defined on the NetCDF Conventions page. Is that really allowed? The sentence following: "The conventions directory name is currently interpreted relative to the directory pub/netcdf/ Conventions/ on the host machine ftp.unidata.ucar.edu." Seems to restrict the meaning even further to one that is implementation specific to the UNIDATA data server. That seems even more out of place on a conventions definition document.
I proclaim myself bewildered. Help and comments would be greatly appreciated.
Nathan On Jan 21, 2010, at 10:57 AM, Bob Simons wrote:
Please leave "Metadata_Conventions" as is.The problem is that the widely used CF convention specifies that the value of "Conventions" should be just "CF-1.4" and that the value is sometimes interpreted as a directory name. So it can't be a list of conventions. Seehttp://cf-pcmdi.llnl.gov/documents/cf-conventions/1.4/cf-conventions.html#identification-of-conventionsSo it is useful to have a separate "Metadata_Conventions" attribute which can be a comma-separated list of convention names, e.g., "COARDS, CF-1.4, Unidata Dataset Discovery v1.0". See http://www.unidata.ucar.edu/software/netcdf-java/formats/DataDiscoveryAttConvention.html .The misuse of "Conventions" at the ERD site was my mistake. I am working to change it to (for most datasets)Conventions : CF-1.4 Metadata_Conventions: COARDS, CF-1.4, Unidata Dataset Discovery v1.0 That's my $0.02. On 1/21/2010 10:36 AM, Nathan Potter wrote:Greetings, Any idea how many people are using the UNIDATA's NetCDF Attribute Convention for Dataset Discovery??If Roy's site is the primary (only?) example of it in actual use, and we accept Benno's point that the name attribute *Metadata_Conventions* isredundant, should we not consider amending the draft to change the attribute name from *Metadata_Conventions* to *Conventions*? (Assuming that it hasn't been push passed the draft spec: Dataset Discovery NetCDF Attribute Convention<http://www.unidata.ucar.edu/software/netcdf-java/formats/DataDiscoveryAttConvention.html >)If we don't change it might we amend the draft to explicitly make the attributes *Metadata_Conventions* and *Conventions* synonymous? Nathan On Jan 14, 2010, at 9:44 AM, Roy Mendelssohn wrote:There are metadata in our files that follows all of those conventions.In trying to relay that act, we felt this was the best way to relay that fact. So you will find the metadata required for CF, the Coastwatch conventions, and the Unidata Data Discovery Conventions. -Roy On Jan 14, 2010, at 9:40 AM, Benno Blumenthal wrote:OK, again trying desperately to understand your cryptic e-mails, http://thredds1.pfeg.noaa.gov/thredds/dodsC/satellite/SW/chla/1day.das has many of those attributes. You did, however, say String Conventions "COARDS, CF-1.0, Unidata Dataset Discovery v1.0, CWHDF"; whereas the document suggested looking for String Metadata_Conventions = "Unidata Dataset Discovery v1.0";What you are doing, of course, makes sense. Did the original documentget corrected over time? Benno On Thu, Jan 14, 2010 at 12:31 PM, Roy Mendelssohn <Roy.Mendelssohn@xxxxxxxx <mailto:Roy.Mendelssohn@xxxxxxxx>> wrote:No we use it extensively. Look at any of he satellite data at our TDS (http://oceanwatch.pfeg.noaa.gov/thredds/catalog.html). It is just since this is not automatically produced by the TDS that we have a program of our own that generates our catalogs. -Roy On Jan 14, 2010, at 9:18 AM, Benno Blumenthal wrote:So, to be really concrete, despite this convention of using netcdfattributes to insert metadata which you just pointed us to, you don't use it at all, you just scan your netcdf files yourself and generate the TDS XML directly. Benno On Thu, Jan 14, 2010 at 12:14 PM, Roy Mendelssohn<Roy.Mendelssohn@xxxxxxxx <mailto:Roy.Mendelssohn@xxxxxxxx>> wrote:We did this "by hand" (well actually we have a program that does it) in generating our catalogs not certain ow others do it. -Roy On Jan 14, 2010, at 8:56 AM, Nathan Potter wrote:Roy, Briefly scanning that page it looks like this gist of it is that one could use NcML to add/complete a "Unidata Dataset Discoveryv1.0" set of metadata to a data set. THis could then be harvestedby the TDS, or by other software that understood the "Unidata Dataset Discovery v1.0" convention. Is that the general idea? N On Jan 14, 2010, at 8:41 AM, Roy Mendelssohn wrote:Hi Nathan: Look at: http://www.unidata.ucar.edu/software/netcdf-java/formats/DataDiscoveryAttConvention.html -Roy On Jan 14, 2010, at 8:33 AM, Nathan Potter wrote:Greetings, I have some questions about the origin of the thredds:geospaptialCoverage element that is commonly found in THREDDS catalogs. It is my understanding that: - The TDS can generate this metadata element by interrogating certain types of source data files.- People that write their own THREDDS catalog files to be servedby the TDS can add the thredds:geospaptialCoverage metadata directly to their catalogs (using whatever process they wish). Is the thredds:geospaptialCoverage also something that can be added through normal channels in NcML augmented data sets? = = = Nathan Potter ndp at opendap.org OPeNDAP, Inc. +1.541.231.3317 _______________________________________________ thredds mailing list thredds@xxxxxxxxxxxxxxxx <mailto:thredds@xxxxxxxxxxxxxxxx> For list information or to unsubscribe, visit: http://www.unidata.ucar.edu/mailing_lists/**********************"The contents of this message do not reflect any position of theU.S. Government or NOAA." ********************** Roy Mendelssohn Supervisory Operations Research Analyst NOAA/NMFS Environmental Research Division Southwest Fisheries Science Center 1352 Lighthouse Avenue Pacific Grove, CA 93950-2097 e-mail: Roy.Mendelssohn@xxxxxxxx <mailto:Roy.Mendelssohn@xxxxxxxx> (Note new e-mail address) voice: (831)-648-9029 fax: (831)-648-8440 www: http://www.pfeg.noaa.gov/ "Old age and treachery will overcome youth and skill." "From those who have been given much, much will be expected"= = = Nathan Potter ndp at opendap.org OPeNDAP, Inc. +1.541.231.3317********************** "The contents of this message do not reflect any position of the U.S. Government or NOAA." ********************** Roy Mendelssohn Supervisory Operations Research Analyst NOAA/NMFS Environmental Research Division Southwest Fisheries Science Center 1352 Lighthouse Avenue Pacific Grove, CA 93950-2097e-mail: Roy.Mendelssohn@xxxxxxxx <mailto:Roy.Mendelssohn@xxxxxxxx>(Note new e-mail address) voice: (831)-648-9029 fax: (831)-648-8440 www: http://www.pfeg.noaa.gov/ "Old age and treachery will overcome youth and skill." "From those who have been given much, much will be expected" -- Dr. M. Benno Blumenthal benno@xxxxxxxxxxxxxxxx <mailto:benno@xxxxxxxxxxxxxxxx> International Research Institute for climate and society The Earth Institute at Columbia University Lamont Campus, Palisades NY 10964-8000 (845) 680-4450********************** "The contents of this message do not reflect any position of the U.S. Government or NOAA." ********************** Roy Mendelssohn Supervisory Operations Research Analyst NOAA/NMFS Environmental Research Division Southwest Fisheries Science Center 1352 Lighthouse Avenue Pacific Grove, CA 93950-2097 e-mail: Roy.Mendelssohn@xxxxxxxx <mailto:Roy.Mendelssohn@xxxxxxxx> (Note new e-mail address) voice: (831)-648-9029 fax: (831)-648-8440 www: http://www.pfeg.noaa.gov/ "Old age and treachery will overcome youth and skill." "From those who have been given much, much will be expected"-- Dr. M. Benno Blumenthal benno@xxxxxxxxxxxxxxxx <mailto:benno@xxxxxxxxxxxxxxxx> International Research Institute for climate and society The Earth Institute at Columbia University Lamont Campus, Palisades NY 10964-8000 (845) 680-4450**********************"The contents of this message do not reflect any position of the U.S.Government or NOAA." ********************** Roy Mendelssohn Supervisory Operations Research Analyst NOAA/NMFS Environmental Research Division Southwest Fisheries Science Center 1352 Lighthouse Avenue Pacific Grove, CA 93950-2097 e-mail: Roy.Mendelssohn@xxxxxxxx <mailto:Roy.Mendelssohn@xxxxxxxx> (Note new e-mail address) voice: (831)-648-9029 fax: (831)-648-8440 www: http://www.pfeg.noaa.gov/ "Old age and treachery will overcome youth and skill." "From those who have been given much, much will be expected"= = = Nathan Potter ndp at opendap.org OPeNDAP, Inc. +1.541.231.3317 _______________________________________________ thredds mailing list thredds@xxxxxxxxxxxxxxxx For list information or to unsubscribe, visit: http://www.unidata.ucar.edu/mailing_lists/-- Sincerely, Bob Simons IT Specialist Environmental Research Division NOAA Southwest Fisheries Science Center 1352 Lighthouse Ave Pacific Grove, CA 93950-2079 Phone: (831)658-3205 Fax: (831)648-8440 Email: bob.simons@xxxxxxxx The contents of this message are mine personally and do not necessarily reflect any position of the Government or the National Oceanic and Atmospheric Administration. <>< <>< <>< <>< <>< <>< <>< <>< <>< _______________________________________________ thredds mailing list thredds@xxxxxxxxxxxxxxxx For list information or to unsubscribe, visit: http://www.unidata.ucar.edu/mailing_lists/
= = = Nathan Potter ndp at opendap.org OPeNDAP, Inc. +1.541.231.3317
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