Re: Paper on OpenDAP

Hi all,

I just wanted to dig a bit deeper into the BUFR issue.

Does anyone know of a Java library for reading BUFR data? I looked around a bit but didn't find anything. The reason I ask is that the netCDF-java 2.2 library (nj22) has an interface for allowing other data formats to be read through the nj22 API. We've used this to add reading of several non-netcdf formats to nj22 (GRIB-1, GRIB-2, GINI, NIDS, NEXRAD level II, e.g.). If there is a java library out there it might not be too hard to add BUFR reading to nj22.

The interface is ucar.nc2.IOServiceProvider. We probably need to work on the documentation but there are several example implementations in the nj22 code. If anyone wants to take a look at this, we could advise and (as time permits) assist. Once an IOSP was done, the TDS could serve the data out through OPeNDAP.

Ethan

Tennessee Leeuwenburg wrote:

Just some off-the-cuff responses.

The GODAE project is worth looking into here -- they have adopted OpenDAP and CF. I don't know how much activity the project has. There seems to be a difference between USGODAE and the vanilla flavour. At any rate, they don't seem to have published anything of significant for a couple of years, but the project is a really nice idea.

Here in the Bureau, we have a moderate degree of standardisaton on COARDS, but it's not an absolute rule.

The "easiest" way might be to support some particular convention in the output, with the server being able to convert to that from a number of different input conventions. For example, write code that will take either a COARDS or CF input file, and do the relevant modifications to the semantic-structure to present consistent output. That at least would greatly simplify the task of visualisation (for example). If coupled with a good generic data viewer (like IDV), then people would me even more inclined to adopt the standard.

Here at the Bureau the biggest obstacle is the lack of a BUFR interpreter for OpenDAP / thredds. This is a big deal for us, and we're going to have to go with a hybrid solution instead of using OpenDAP across the board. BUFR is an acronym for Binary Universal File Representation, and has been adopted by the World Met Organisation as a standard for obvervational data. It's a complete hassle to deal with, because the level of software support is low.

The other thing I thought would be cool (while we're throwing ideas around like popcorn) would be if Thredds was also a web service, with a WSDL and so forth.

Do any such conventions exist for OpenDAP?



No. The idea is to let different disciplines impose whatever structure they want on top of OPeNDAP. The more appropriate question would be "Does the oceanographic (or the Earth Science) community have any such convention?" Unfortunately, the answer is again no. That is my fault. I should have recommended one a long time ago. I think that COARDS (or CF) would be an excellent starting point and COARDS is becoming a de facto standard in that many data providers use it. I was reluctant to impose COARDS on the oceanographic use of the system since that would mean the reordering of some archives which could be very costly. I prefer a modified C COARDS, one that does not adhere to the semantic structure, but does adhere to the rest of the standard.

Here at BOM we more or less have our conventions agreed on for my particular project, but if there were any recommended best practise it could be interesting.



What do you think of adopting COARDS or CF? Would one or the other address all of your data sets? If not, what is missing? If it could, but your would rather not adopt it, it would really be useful to know why and to know what you guys have adopted and why. I am hoping that the Marine Metadata effort comes up with a recommendation for the oceanographic community. I'm not sure what is being done for the meteorological community, but it would be great if there was a similar effort (to the Marine Metadata program) and if they came up with a recommendation.

Peter


Cheers,
-Tennessee

--
 Peter Cornillon
   Graduate School of Oceanography     -  Telephone: (401) 874-6283
University of Rhode Island - Fax: (401) 874-6728 Narragansett, RI 02882 - E-mail: pcornillon@xxxxxxxxxxx



--
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/
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