>> 2) In our applications we need more than one unlimitted dimension. As far
as
>> I see netCDF allows only one.
>
>That's right, and the reason for that limitation is again an engineering
>trade-off, to provide efficient access to cross-sections of data. We know
>of no implementation that permits multiple unlimited dimensions, efficient
>access to orthogonal cross-sections of data, and the ability to later
append
>data along any of the unlimited dimensions.
>
>> Will there be changes in the future solving the two problems or could we
>> solve them ourselves? Do others have these problems? Is anybody from
Unidata
>> listening?
>
>We have investigated ways to remove the restriction on a single unlimited
>dimension, but these appear to require adding other new restrictions to
>netCDF data access. For example, by restricting the writing of
>multidimensional arrays to occur in the same order as they are stored,
>rather than in arbitrary order as is now allowed, multiple unlimited
>dimensions might be (weakly) supported. Another approach requires garbage
>collection, to recover unused locations so that a file doesn't grow
>quadratically in size as a single vector is extended linearly along an
>unlimited dimension.
I am by no means an expert on netcdf or data formats and storage, but as a
user I would gladly take the restriction that multidimensional arrays be
written in the same order as they are stored in order to get (even weak)
netcdf support for multiple unlimited dimensions.
Phil Miller
philip.miller@xxxxxxxxxx
