3.4 Using the Aggregation Server as a NetCDF server

The Aggregation Server can also serve NetCDF files as OPeNDAP datasets without aggregating them. In this case, specifying the internal service is harder because we don't have an aggregation or fileAccess element to specify the serviceName, and putting a serviceName attribute on the dataset element would change the Dataset URL, not the internal file location. To specify a local NetCDF file, use a property element whose name is internalService and whose value is the name of the internal service to use, as in Example 8.

...
<service name="local" serviceType="NetCDF" 
    base="file:///E:/data/grids/GSO-derived/"/>
<service name="loco" serviceType="NetCDF" 
    base="file:///E:/data/grids/UFO-derived/"/>
<dataset name="Non-Aggregated Netcdf Files" serviceName="this">
  <property name="internalService" value="local"/>
  <dataset name="RUC/516" urlPath="516_ruc.nc"/>
  <dataset name="RUC/517" urlPath="517_ruc.nc"/>
  <dataset name="RUC/518" urlPath="518_ruc.nc">
    <property name="internalService" value="loco"/>
  </dataset>
</dataset>

In Example 8, the first property element sets up a default value for the datasets, while the second property tag specifies an exception to the default. The result is that the first two internal files of the dataset come from the "local" NetCDF service, and the third from the "loco" NetCDF service. The only real difference is the base path in which the Aggregation Server looks for the files. Setting up a default in this manner is not essential, but it can save you some typing.

NOTE: When the Aggregation Server is used to serve non-aggregated netCDF files, the urlPath of the dataset is used in both the external Dataset URL and the internal File URL. Therefore dataset URLs for NetCDF files are not arbitrary, since they must map to real files accessible to the Aggregation Server. However the urlPath must still be unique within the catalog.

<catalog name="Example OPeNDAP Aggregation Server Catalog" version="0.6" >
  <dataset name="Top level dataset" dataType="Grid" serviceName="this">
    <service name="local" serviceType="NetCDF" base="file:///MyDataPath"/>
    <property name="internalService" value="local"/>
    ...
  </dataset>
</catalog>