Adding a service to a remotely served dataset
Roy Mendelssohn
Roy.Mendelssohn at noaa.gov
Mon Jul 9 10:38:55 MDT 2007
Very interesting. Thanks John. Is this in the version we have
(3.16.13) or is it in a new download?
When we get a chance, we will test this as it is a feature we would
like to be able to add.
Regards,
-Roy
On Jul 9, 2007, at 9:32 AM, John Caron wrote:
> We made an extension of the WCS Dataset URL format to allow the TDS
> to serve remote datasets. Identify the dataset by adding the
> parameter dataset whose value is a URL:
>
> http://servername:8080/thredds/wcs?dataset=datasetURL&
>
> The URL must be a dataset readable by the NetCDF-Java library,
> typically an OPeNDAP dataset on another server. It must have
> gridded data, with identifiable coordinate systems, etc. For
> example, an OPeNDAP URL might be
>
> http://las.pfeg.noaa.gov/cgi-bin/nph-dods/data/oceanwatch/nrt/gac/
> AG14day.nc
> This can be served remotely as a WCS dataset with this URL:
>
> http://servername:8080/thredds/wcs?dataset=http://
> las.pfeg.noaa.gov/cgi-bin/nph-dods/data/oceanwatch/nrt/gac/AG14day.nc&
>
>
> This is non-standard WCS; we havent emphasized this feature until
> we have a chance to review security implications. The WCS service
> now if off by default, and must explicitly be turned on in
> threddsConfig.xml, mostly because of this feature. We should
> probably seperately allow users to enable/disable "remote WCS access".
>
>
> Oliver Newell wrote:
>> Hi Roy -
>> FYI - We're currently experimenting with implementing WCS
>> services, and the same requirement (wish?) as what you're
>> describing has been raised. Basically, the need to discover a data
>> set via a cataloging mechanism (THREDDS, an OGC catalog, a DOD
>> NCES catalog) and then be able to access it via a WCS that resides
>> somewhere on the network. My initial take on it is that since WCS
>> data access requests work with unique identifiers (not URLs), this
>> limits the capabilities of the service in the sense that the Id-to-
>> resource (data file or db) mapping is managed locally by the WCS.
>> In other words, the WCS has to 'know about' the resource in
>> advance of the request, in order to do the mapping.
>> I think the WCS service should support a mode of operation where a
>> resource's URL is included in the requests to the service, in
>> order to support the external WCS concept. I think it is still
>> important to maintain the Id as a separate entity, so it is not
>> just a question of using a URL for the coverage identifier, though
>> that idea might be tempting.
>> The idea needs flushing out a bit, but it is still early enough in
>> WCS's development that changes like this can be incorporated into
>> the spec via the OGC working group (my opinion). It definitely
>> seems like it would be a useful capability to address the
>> situation you describe.
>> -Oliver
>> Roy Mendelssohn wrote:
>>> Hi Glenn:
>>>
>>> No problem. But we were interested in the general problem, as
>>> there are other datasets which also do not have WCS and which we
>>> would like to add it, rather than trying to get each of them to
>>> add it (Some just have an OPeNDAP server, not a THREDDS
>>> server). Yours allowed me to give Ethan a concrete example so he
>>> could look at the catalogs.
>>>
>>> Thanks,
>>>
>>> -Roy
>>> On Jul 9, 2007, at 7:52 AM, Glenn.Rutledge wrote:
>>>
>>>> Hello Roy-
>>>> That particular dataset will be turned on shortly via WCS. That
>>>> was an oversight. Nice to have users telling us where we need
>>>> stuff! Glenn
>>>>
>>>> Ethan Davis wrote the following on 7/6/2007 6:02 PM:
>>>>> Hi Roy,
>>>>>
>>>>> Looks like you are referencing NCDC catalogs rather than
>>>>> serving the datasets yourself. So, users would get redirected
>>>>> to the NCDC server and access the data through the NCDC server.
>>>>> So, as things stand, NCDC would have to add the WCS service.
>>>>>
>>>>> You could point to each NCDC dataset with an NcML wrapper and
>>>>> actually serve the data from your server rather than
>>>>> redirecting to NCDC. If you did that, you could add the WCS
>>>>> service. However, the performance wouldn't be as good as direct
>>>>> from NCDC.
>>>>>
>>>>> I'm afraid I don't know about the WCS request for a time range.
>>>>> So, I'll leave that for others to answer.
>>>>>
>>>>> Ethan
>>>>>
>>>>> Roy Mendelssohn wrote:
>>>>>> Hi Ethan:
>>>>>>
>>>>>> I am not certain I follow. To be more specific, look at:
>>>>>>
>>>>>> http://oceanwatch.pfeg.noaa.gov/thredds/catalog.html
>>>>>>
>>>>>> and scroll down to the datasets " Remote test to Nomads
>>>>>> THREDDS catalog", which is actually on a THREDDS server on an
>>>>>> NCDC computer. They are remotely served through catalogs.
>>>>>> Can we add the WCS service on our end, or will it only work if
>>>>>> NCDC adds the WCS service.
>>>>>>
>>>>>> While I have your attention, I have not been able to get a
>>>>>> straight answer if there is a way to send the WCS request to
>>>>>> get a time range, rather than a single time, and if so what is
>>>>>> the syntax for that.
>>>>>>
>>>>>> Thanks,
>>>>>>
>>>>>> -Roy
>>>>>>
>>>>>> On Jul 6, 2007, at 11:24 AM, Ethan Davis wrote:
>>>>>>
>>>>>>> Hi Roy,
>>>>>>>
>>>>>>> If you are actually serving the dataset through your server
>>>>>>> (which it sounds like you are since you mention existing NcML
>>>>>>> for the dataset) rather than providing a link in your catalog
>>>>>>> to the remote server, I believe you can simply add the WCS
>>>>>>> service to your TDS configuration catalog and serve the data
>>>>>>> via WCS. It shouldn't require any changes to the NcML, just
>>>>>>> to the service element in the catalog.
>>>>>>>
>>>>>>> Of course, this depends on the dataset meeting the WCS server
>>>>>>> requirements, e.g., evenly spaced grid.
>>>>>>>
>>>>>>> I'm not sure how it would perform. But I'll leave it for John
>>>>>>> to respond on that.
>>>>>>>
>>>>>>> Ethan
>>>>>>>
>>>>>>> Roy Mendelssohn wrote:
>>>>>>>> Hi:
>>>>>>>>
>>>>>>>> The question for today is if our TDS is "serving" a dataset
>>>>>>>> remotely (ie. the remote site has their own TDS and we just
>>>>>>>> link indirectly to it), can we add a service to our version
>>>>>>>> that they don't have (just like we can aggregate a remote
>>>>>>>> dataset that is not aggregated). In particular the remote
>>>>>>>> dataset only has an OPeNDAP response, but we would like to
>>>>>>>> be able to respond to both an OPeNDAP and a WCS response.
>>>>>>>>
>>>>>>>> If we change our NcML appropriately, will that work?
>>>>>>>>
>>>>>>>> Thanks in advance,
>>>>>>>>
>>>>>>>> -Roy
>>>>>>>>
>>>>>>>> **********************
>>>>>>>> "The contents of this message do not reflect any position of
>>>>>>>> the U.S. Government or NOAA."
>>>>>>>> **********************
>>>>>>>> Roy Mendelssohn
>>>>>>>> Supervisory Operations Research Analyst
>>>>>>>> NOAA/NMFS
>>>>>>>> Environmental Research Division Southwest Fisheries
>>>>>>>> Science Center
>>>>>>>> 1352 Lighthouse Avenue
>>>>>>>> Pacific Grove, CA 93950-2097
>>>>>>>>
>>>>>>>> e-mail: Roy.Mendelssohn at noaa.gov (Note new e-mail address)
>>>>>>>> voice: (831)-648-9029
>>>>>>>> fax: (831)-648-8440
>>>>>>>> www: http://www.pfeg.noaa.gov/
>>>>>>>>
>>>>>>>> "Old age and treachery will overcome youth and skill."
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> ===============================================================
>>>>>>>> ===============
>>>>>>>> To unsubscribe thredds, visit:
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>>>>>>>> ===============================================================
>>>>>>>> ===============
>>>>>>>
>>>>>>> --Ethan R. Davis Telephone:
>>>>>>> (303) 497-8155
>>>>>>> Software Engineer Fax:
>>>>>>> (303) 497-8690
>>>>>>> UCAR Unidata Program Center E-mail:
>>>>>>> edavis at ucar.edu
>>>>>>> P.O. Box 3000
>>>>>>> Boulder, CO 80307-3000 http://
>>>>>>> www.unidata.ucar.edu/
>>>>>>> ----------------------------------------------------------------
>>>>>>> -----------
>>>>>>>
>>>>>>>
>>>>>>
>>>>>> **********************
>>>>>> "The contents of this message do not reflect any position of
>>>>>> the U.S. Government or NOAA."
>>>>>> **********************
>>>>>> Roy Mendelssohn
>>>>>> Supervisory Operations Research Analyst
>>>>>> NOAA/NMFS
>>>>>> Environmental Research Division Southwest Fisheries Science
>>>>>> Center
>>>>>> 1352 Lighthouse Avenue
>>>>>> Pacific Grove, CA 93950-2097
>>>>>>
>>>>>> e-mail: Roy.Mendelssohn at noaa.gov (Note new e-mail address)
>>>>>> voice: (831)-648-9029
>>>>>> fax: (831)-648-8440
>>>>>> www: http://www.pfeg.noaa.gov/
>>>>>>
>>>>>> "Old age and treachery will overcome youth and skill."
>>>>>>
>>>>>>
>>>>>
>>>>
>>>> --Glenn K. Rutledge
>>>> Services Team Leader
>>>> Remote Sensing and Applications Division
>>>> NOMADS Project Manager
>>>> National Oceanic and Atmospheric Administration
>>>> National Climatic Data Center
>>>> Asheville NC 28801
>>>> Phone: (828) 271-4097
>>>> Fax: (828) 271-4328
>>>>
>>>> NOMADS: http://nomads.ncdc.noaa.gov/
>>>>
>>>
>>> **********************
>>> "The contents of this message do not reflect any position of the
>>> U.S. Government or NOAA."
>>> **********************
>>> Roy Mendelssohn
>>> Supervisory Operations Research Analyst
>>> NOAA/NMFS
>>> Environmental Research Division Southwest Fisheries Science Center
>>> 1352 Lighthouse Avenue
>>> Pacific Grove, CA 93950-2097
>>>
>>> e-mail: Roy.Mendelssohn at noaa.gov (Note new e-mail address)
>>> voice: (831)-648-9029
>>> fax: (831)-648-8440
>>> www: http://www.pfeg.noaa.gov/
>>>
>>> "Old age and treachery will overcome youth and skill."
>>>
>>>
>>>
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**********************
"The contents of this message do not reflect any position of the U.S.
Government or NOAA."
**********************
Roy Mendelssohn
Supervisory Operations Research Analyst
NOAA/NMFS
Environmental Research Division
Southwest Fisheries Science Center
1352 Lighthouse Avenue
Pacific Grove, CA 93950-2097
e-mail: Roy.Mendelssohn at noaa.gov (Note new e-mail address)
voice: (831)-648-9029
fax: (831)-648-8440
www: http://www.pfeg.noaa.gov/
"Old age and treachery will overcome youth and skill."
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