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Re: [thredds] Using the NC4 String type for a variable containing a "cf_role" attribute

  • Subject: Re: [thredds] Using the NC4 String type for a variable containing a "cf_role" attribute
  • From: John Caron <caron@xxxxxxxxxxxxxxxx>
  • Date: Mon, 16 Dec 2013 09:21:20 -0700
strictly speaking yes, but if thats not of paramount concern, the community needs to try out new technology and standard ways of doing things; that is, we have to lead CF, not the other way around. 

On 12/16/2013 8:53 AM, Signell, Richard wrote:

John,
Even though you will modify NJ to handle this, you are saying: If producers want to deliver CF-compliant data, they should be not be writing string variables. 

Right?

Thanks,
Rich
On Mon, Dec 16, 2013 at 9:52 AM, John Caron <caron@xxxxxxxxxxxxxxxx <mailto:caron@xxxxxxxxxxxxxxxx>> wrote: 

    On 12/12/2013 1:27 PM, Kyle Wilcox wrote:

    I have two files where the only difference is the variable type
    of the "feature_type_instance" variable.

    When using a Char array, it works just fine.
    When using a String, NCJ fails to find a StructureRecord:

    java.lang.IllegalStateException: Cant find Structure record
    Â  Â  at
    ucar.nc2.ft.point.standard.Table$TableStructure.<init>(Table.java:253)
    Â  Â  at ucar.nc2.ft.point.standard.Table.factory(Table.java:110)
    Â  Â  at
    ucar.nc2.ft.point.standard.NestedTable.<init>(NestedTable.java:98)
    Â  Â  at
    ucar.nc2.ft.point.standard.TableAnalyzer.analyze(TableAnalyzer.java:406)
    Â  Â  at
    ucar.nc2.ft.point.standard.TableAnalyzer.factory(TableAnalyzer.java:294)
    Â  Â  at
    
ucar.nc2.ft.point.standard.PointDatasetStandardFactory.isMine(PointDatasetStandardFactory.java:114)
    Â  Â  at
    
ucar.nc2.ft.FeatureDatasetFactoryManager.wrap(FeatureDatasetFactoryManager.java:272)
    Â  Â  at
    
ucar.nc2.ft.FeatureDatasetFactoryManager.open(FeatureDatasetFactoryManager.java:243)



    You can try loading each file into the FeatureTypes/PointFeature
    tab to see the stacktrace from the String file (I've attached them).

    Based on CF docs
    
(http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.6/cf-conventions.html#coordinates-metadata)
    it states:
    "The variable carrying the cf_role attribute may have any data type."


    Is this a bug in NCJ?

    Thanks,
    Kyle


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    Hi Kyle:

    CF only deals with classic netcdf data model, which doesnt have
    Strings. However, the CDM deals with the extended model wherever
    possible, so yes, i think this is a bug and we'll get it fixed.

    John

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--
Dr. Richard P. Signell   (508) 457-2229
USGS, 384 Woods Hole Rd.
Woods Hole, MA 02543-1598
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