Hi Heiko,
Heiko Klein wrote:
I'm evaluating the usage of thredds for an EU project
http://www.ecmwf.int/research/EU_projects/GEMS/
I installed the 2.0 version and was able to browse some pages and see
some data, but I still have some more general questions:
What are the main advantages of thredds against opendap?
THREDDS is not a replacement for OPeNDAP. THREDDS adds cataloging
capabilities on top of various data access systems. The aggregation
server (and the upcoming 3.1 THREDDS server) provide both OPeNDAP and
THREDDS services.
I see a lot of XML files and the last s in thredds is for services:
What is the relation between thredds and web-services
(http://www.w3.org/2002/ws/) or REST
(http://www.xfront.com/REST-Web-Services.html).
Well, THREDDS catalogs are XML documents available over HTTP. Catalogs
can reference other catalogs and can also provide links for accessing
datasets. Besides catalogs, there are a number of other THREDDS services
available. For instance, the Dataset Query Capabilities (DQC) allows
users to request a subset of a dataset collection. Current THREDDS
services don't use any of the WS frameworks, so I'd say THREDDS is built
on "web services" but not "Web Services".
Does thredds include a opendap server (didn't manage to get that
working), or is thredds just able to distribute data via an external
opendap server. If yes: Is the thredds opendap server able to serve as
much data as the generic opendap servers, i.e. grib,hdf4,hdf5?
The current 2.0 THREDDS server includes the aggregation server which can
serve netCDF files (and OPeNDAP dataset) individually or aggregated. The
upcoming 3.1 THREDDS Data Server can serve all the data that the
netCDF-java library can read (nc, GRIB-1 and -2, most HDF5, NEXRAD level
II and III, and a few others; see the netCDF-java page for more details
,http://www.unidata.ucar.edu/software/netcdf-java/).
What is the status of thredds (3.0?), the aggregation server and the
query language to search the aggr. server?
The THREDDS Data Server (TDS) 3.1 will be released shortly. The
aggregation server is being refactored and will be folded into the TDS
at some future date. I'm not sure what you mean by "query langague to
search the agg server". The DQC (which I mentioned above) is the only
query language we are working on and it is not widely used at this
point. But it isn't specific to the agg server.
Hope this clears things up. Let me know if you have other questions.
Ethan
Best regards,
Heiko
--
Dr. Heiko Klein Tel. + 47 22 96 33 44
Air pollution Section/Research Department Fax. + 47 22 69 63 55
Norwegian Meteorological Institute http://www.met.no
P.O. Box 43 Blindern 0313 Oslo NORWAY http://www.emep.int
--
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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