Due to the current gap in continued funding from the U.S. National Science Foundation (NSF), the NSF Unidata Program Center has temporarily paused most operations. See NSF Unidata Pause in Most Operations for details.
Due to the current gap in continued funding from the U.S. National Science Foundation (NSF), the NSF Unidata Program Center has temporarily paused most operations. See NSF Unidata Pause in Most Operations for details.
Hi Rich, On 9/24/06, Rich Signell <rsignell@xxxxxxxx> asked: > Could NetCDF-Java be used to mimic each function in the NetCDF-3 C API > or are there certain functions that just can't be accomplished in the > NetCDF Java API. Like reentering define mode. There are currently things you can do in the in the netCDF-3 C or Fortran API that can't be accomplished with NetCDF Java. Reentering define mode is one, and another more basic example is modifying attribute values or deleting attributes. In netCDF Java, attributes are considered immutable. In fact, the file schema is considered immutable, as the User's Guide says: A new NetCDF file is created with the createNew factory method. The structural metadata (groups, dimensions, attributes and variables) can only be added at creation time. Thus, when a file is first opened, it is in define mode where these may be added. Once create() is called, the dataset structure is immutable. After create() has been called you can then write the data values. See example in the Appendix. Permitting the equivalent of define mode in which variables, dimensions, and attributes can be added to an existing netCDF file, is a convenience available in the C and Fortran modes. But this convenience comes at a cost: a user can easily cause all the data in the file to be copied with an innocent looking operation such as adding a variable or assigning a new value to an attribute for which space is not available in the file header. To make such expensive operations more visible, the Java interface doesn't hide the underlying mechanisms. If doing something will require essentially copying the file, the Java interface requires that you explicitly copy the file, so you are aware of the performance implications of calling methods. When we first decided to make the file schema immutable in the Java interface, I argued on the other side, that we should exactly duplicate all the functionality of the C interface. But I think I've been proven wrong, because we have gotten very few requests for operations not permitted in the Java interface, like renaming variables with a longer name or adding new attributes. The single exception is changing attribute values. There have been enough requests for this capability that we may add it to netCDF Java. (John Caron may provide corrections if I've gotten any of the details wrong, but he's away from his email for the next week or so.) --Russ _____________________________________________________________________ Russ Rew UCAR Unidata Program russ@xxxxxxxxxxxxxxxx http://www.unidata.ucar.edu ============================================================================== To unsubscribe netcdf-java, visit: http://www.unidata.ucar.edu/mailing-list-delete-form.html ==============================================================================
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