Re: [netcdf-java] THREDDSMetadata in NetCDF files

Hi Martin,

In your original posting you mentioned a goal of creating better ISO support for netCDF in Geotoolkit. I'm assuming that the focus is on supporting local NetCDF files that geotoolkit reads and then maps to the ISO metadata classes, is that correct?

If this is the case, I don't think that using UnidatataDD2MI.xsl is a good initial reference point for your task as there are some implementation details that are creating some confusion. ncISO has two implementations, in the first it acts as a client to a THREDDS server and accesses data/metadata contained in NetCDF via the NetcdfDataset object (using OpenDAP) AND has access to THREDDS metadata. In the second implementation, it acts as a service embedded within THREDDS and again has access to the local file (or virtual dataset) and THREDDS metadata.

If my assumption is correct about your goal of providing better ISO support for local netCDF files in Geotoolkit, then I would rely mostly on the ACDD convention mapping located here:

The xsl mapping could then be useful in terms of looking at any precedence issues, when for example, you have spatial and temporal extent information coming from the NetCDF axis that conflicts with information contained in the file attributes.


On 10/6/2011 9:18 AM, Martin Desruisseaux wrote:
Hello again Dave

Sorry to bother you for what may be a trivial question (I'm also unfamiliar with XPath, in case my question is related to XPath syntax)...

On the following page:

For example we can read for the "creator_name" attribute a "metadata/creator/name" THREDDS path. But I'm not sure how to interpret this path. Is it a "name" attribute inside a "creator" group which is itself inside a "metadata" group? What means the @ character that we can read in some place? (for example "metadata/creator/contact@url")?

Later on the same page, there is a NcML example which contains (simplified):
<group name="THREDDSMetadata">
   <attribute name="id" value="crm_v1" />
   <attribute name="creator_name" value="David Neufeld"/>
   <attribute name="creator_email" value="David.Neufeld@xxxxxxxx"/>

But this doesn't seem consistent with my previous paragraph:

    * The group name is "THREDDSMetadata", not "metadata"
    * There is no "creator" sub-group with a "name" attribute, but
      instead a "creator_name" attribute.

Furthermore the file seems to give yet an other picture, since the path is defined as (omitting the global attribute):


Which I interpret as "name" attribute inside a "creator" group, itself inside a "creators" group (does it means that we can have many groups named "creator" inside "creators" in a NetCDF file? I know we can do that in XML, but is it allowed in NetCDF too?), itself inside "THREDDSMetadata" group.

So I'm a little bit confused... Maybe my understing is not correct? What are the THREDDS attributes we are supposed to look at?


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