Hi Markus,
Both NcML and FeatureCollections have the concept of a "prototype dataset"
[1][2]. It is the dataset from which metadata for the aggregation is taken.
To answer your question, here is a snippet from the FeatureCollections
page, which also applies to NcML aggregation:
The choice of the protoDataset matters when the datasets are not homogenous:
* Global and variable attributes are taken from the prototype dataset.
* If a variable appears in the prototype dataset, it will appear in the
feature collection dataset. If it doesnt appear in other datasets, it will
have missing data for those times.
* If a variable does not appears in the prototype dataset, it will not
appear in the feature collection dataset, even if it appears in other
datasets.
Cheers,
Christian
[1]
http://www.unidata.ucar.edu/software/thredds/current/tds/reference/ThreddsConfigXMLFile.html#Aggregation
[2]
http://www.unidata.ucar.edu/software/thredds/current/tds/reference/collections/FeatureCollections.html
(scroll down to the "protoDataset element" section)
On Mon, Jul 27, 2015 at 3:40 AM, Markus Fiebig <Markus.Fiebig@xxxxxxx>
wrote:
> Dear list members,
>
> a question from someone considering to set up his own THREDDS server:
>
> THREDDS has its own built-in subset service that can make cut-outs from
> its data
> repository going over several original netCDF files and arranging them
> into one
> netCDF file. Let's say that all these original netCDF files conform in all
> co-ordinates etc. such that the subsetting is possible, but that they
> differ in
> certain global attributes. How would the subset service handle this case?
> Would
> it include all the various global attributes correctly with the various
> pertaining data, or would it just discard the global attributes since they
> are
> not homogeneous over the selected data subset?
>
> Best regards,
> Markus
>
> --
> Dr. Markus Fiebig
> Senior Scientist
> Dept. Atmospheric and Climate Research (ATMOS)
> Norwegian Institute for Air Research (NILU)
> P.O. Box 100
> N-2027 Kjeller
> Norway
>
> Tel.: +47 6389-8235
> Fax : +47 6389-8050
> e-mail: Markus.Fiebig@xxxxxxx
> skype: markus.fiebig
>
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