20000717: 20000712: a question

>From: Steve Emmerson <steve@xxxxxxxxxxxxxxxx>
>Organization: UCAR/Unidata
>Keywords: 200007171838.e6HIcxT08419


>> I think this objective remains valid, and perhaps "pluggable semantic
>> parsers" could help us get there, though I don't yet understand
>> exactly what it means.  I once proposed that Steve's netCDF adapter
>> for VisAD could be augmented with a constructor whose signature
>> included a text string making the MathType explicit, i.e., replacing
>> Steve's intelligent guesswork with knowledge of specific netCDF files
>> or conventions.  Is the pluggable semantic parser idea more or less
>> equivalent?
>I wouldn't do it that way.  Instead, I'd have a programatically-settable
>layer above the import layer whose job would be to convert the incoming
>data object(s) into something that is known a priori to be more
>appropriate for the task at hand.  This would separate the semantics of
>the data from the nut-and-bolts of reading it in.

You wouldn't want to read in the entire netCDF file and then pick the
Data object apart, if you already knew the netCDF variables and knew 
the MathType you wanted to return.   That would be unnecessary overhead.

One thing that would be very useful would be to enhance
visad.data.netcdf.Plain so it can return the just MathType of the netCDF
file. Add that to the capability of specifying the MathType of the data
you want to get at as Dave (and others) have requested, and one could
create a netCDF browser GUI that would allow the user to create new
MathTypes and retrieve just data associated with those.

Don Murray                               UCAR Unidata Program
dmurray@xxxxxxxxxxxxxxxx                        P.O. Box 3000
(303) 497-8628                              Boulder, CO 80307
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