Re: 20000712: a question

Hi Don,

Don Murray writes:
 > >From: Bill Hibbard <hibbard@xxxxxxxxxxxxxxxxx>
 > >Organization: SSEC
 > >Keywords: 200007121209.e6CC9eT00155
 > 
 > Mike/Bill -
 > 
 > >> Does anyone know if someone is working on providing DODS data
 > >> reading capability for VisAD?
 > >> http://www.unidata.ucar.edu/packages/dods/index.html
 > >
 > >We discussed this among the folks at SSEC and Unidata.  It
 > >is a question of how similar the Java APIs for DODS and netCDF
 > >are.  I think someone said the C APIs are identical, but that
 > >this is not true for their Java APIs.  At any rate, the trick
 > >would be to exploit the existing netCDF adapter for VisAD to
 > >access DODS servers.
 > >
 > >Perhaps one of the experts from Unidata can comment.
 > 
 > At first glance, one would think they could just use the DODS
 > HTTP request using netCDF format and it should seamlessly go into
 > VisAD.  However, that is not the case because the Java netCDF API
 > does not support access to a remote file using the NetcdfFile class
 > which is what the VisAD netCDF adapter (Plain) uses.

Another reason this wouldn't work on a DODS URL is because the data
returned is not in netCDF format.  (Don: what you and I looked at was
removing the DODS part of the URL and just trying to access a web
accessible netCDF file via HTTP.)  For a DODS access in VisAD to work,
there would have to be some DODS client software on the VisAD end.
Either, as I described in my earlier note, a DODS version of the Java
netCDF library or, now that I think of it, the more direct route of
making a VisAD DODS adaptor that calls the DODS Java API.

We've thought more about the first option than the second because:
option one would also be valuable outside the VisAD community; and
with option two, the use of attribute conventions would have to be
added instead of taking advantage of the netCDF conventions already
in the VisAD netCDF adaptor.

Ethan
-- 
Ethan R. Davis                       Telephone: (303) 497-8155
Software Engineer                    Fax:       (303) 497-8690
UCAR Unidata Program Center          E-mail:    edavis@xxxxxxxx
P.O. Box 3000
Boulder, CO  80307-3000              http://www.unidata.ucar.edu/