Re: [galeon] WCS CF-netCDF profile document

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Hi Stefano et. al.,
Ben and I just made a step towards closing the loop on this conversation through a telephone call. We found ourselves to be wildly in agreement. :-) . Based upon your email below, it sounds like we may all be very close to agreement (ah, the eternal optimist ;-) ...).
On the phone Ben and I agreed to propose the following two actions for the short term. For everyone's comments, please: 

  1. GALEON should issue some form of announcement on its *intention*
to investigate encapsulating the OPeNDAP protocol within WCS (perhaps following the template offered by JPIP). This 
     announcement would be intended to begin to erase the perception of
     a divide between OPeNDAP and WCS as soon as possible.
  2. We should conduct a quick investigation of whether there may be a
     simple approach to embedding OPeNDAP into WCS that can be achieved
     as a very small delta on the draft "WCS CF-netCDF profile
     document" (the subject line of this dialog).  _See the PS below_
     for details about this idea (especially John Caron for TDS
     implementation thoughts)

   - Steve
P.S. Some thoughts on quickly embedding OPeNDAP into the document, "Web Coverage Service (WCS) 1.1 extension for CF-netCDF 3.0 encoding, 1.0": 

   A simplified view of OPeNDAP for purposes of this discussion is that
   it is a transparent mechanism by which an application can use netCDF
   API calls on a remote file.  Thus for any netCDF subset that may be
   derived from a TDS server, there is an OPeNDAP URL that is an
   indirect reference to that same subset.  For example consider the
   dataset coads_climatology.nc, served by TDS at
http://ferret.pmel.noaa.gov/thredds/dodsC/data/PMEL/coads_climatology.nc.html. The dataset contains 12 months of grids for seven different surface 
   met fields.  Imagine a WCS GetCoverage request that would return a
   netCDF file containing global SST for the month of January.  The
   contents of this exact netCDF subset can be expressed by the OPeNDAP
URL: "http://ferret.pmel.noaa.gov/thredds/dodsC/data/PMEL/coads_climatology.nc?COADSX,COADSY,TIME[0:1:0],SST[0:1:0]"; Essentially the netCDF file is just a de-referencing of this URL. An application program that can utilize the netCDF file can (in 
   principal) utilize the URL equivalently.  (I just tested this
   particular example with Ferret and behaved exactly as it would with
   the local file.)

   Now,  the document,  "Web Coverage Service (WCS) 1.1 extension for
   CF-netCDF 3.0 encoding, 1.0", describes a WCS GetCoverage response
   that returns a netCDF _file_ as its payload.  Could we envision a
   small change to this document that described returning an equivalent
   URL instead of the file itself?  Such an approach could open the
   door to OPeNDAP-WCS fusion now (in the document version 1.0).  And
   then in a subsequent version of the document the ideas could be
   fleshed out with discussions of further OPeNDAP protocol issues --
   access control, latency, proxying, streaming, etc.

   I realize this suggestion is awfully "sloppy", when compared to the
   thorough and careful work you have done in the document.  Maybe the
   contrast would be acceptable as long as OPeNDAP is confined to an
   appendix at this point.  There also may be better ways to return the
   OPeNDAP URL -- perhaps as two pieces, separating the base URL from
   the key constraints:

       * base URL:
         
"http://ferret.pmel.noaa.gov/thredds/dodsC/data/PMEL/coads_climatology.nc";
       * key constraint: "SST[0:1:0]"


stefano nativi wrote:

Steve,
I think you raised extremely important issues for the Community and for GALEON.
IMHO, you listed some of the main GALEON objectives: 1) to "open" MetOcean Community models and resources to other Communities in order to face cross-disciplinary challenges; 2) to fill the existing gaps of the Community IT solutions (e.g. to explicit semantics) to leverage the Web potentialities 3) to bridge with the European partners, who have de -jure directives to follow as far as IT is concerned.
In an over-simplified way, I could say: Multi-disciplinary interoperability using IT 


Thank you very much for your valuable comments.

--Stefano
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