[ESIP-CF] Esip-cf Digest, Vol 5, Issue 1
Ted Habermann
ted.habermann at noaa.gov
Wed Feb 1 12:26:02 EST 2012
Upendra et al.,
I agree that User-Defined Types are a potentially very interesting approach
to adding structure to metadata in granules. One of the challenges is that
UDTs have been developed as a tool for describing data structures instead
of attribute structures. In other words, we would need to write metadata
into variables instead of into attributes. I suspect that this would change
the mechanisms we use to write and extract this information considerably...
I have discussed the question of arrays of attributes with Mike Folk from
the HDF group (cc'ed) recently, and plan to follow up on that approach...
If we could extend the idea of UDT's into the attribute space it would be
very cool!
Ted
----------------------------------------------------------------------
>
> Message: 1
> Date: Tue, 31 Jan 2012 15:58:38 -0500
> From: Upendra Dadi <upendra.dadi at noaa.gov>
> To: esip-cf at lists.esipfed.org
> Subject: Re: [ESIP-CF] CF Cluster telecon today
> Message-ID: <4F2855FE.7000500 at noaa.gov>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Hi All,
> I added a link on the Wiki to a netCDF file created by NDBC which
> uses groups.
>
> On a related note, I want to ask this group if they have considered
> using user defined structures in place of groups. As you might be
> knowing that netCDF-4 allows compound types which are based on C struct.
> Compound types along with variable length arrays could often be a good
> substitute for using groups. With regard to CF, incorporating groups, I
> am guessing, is much more challenging than including compound types.
> Anybody disagrees? I am looking for some examples where groups are much
> better suited than using compound types and/or variable length arrays.
> Please let me know if you have one. Thank you!
>
> Upendra
>
> On 1/31/2012 7:11 AM, Raskin, Rob (388M) wrote:
> > This is a reminder that the rescheduled CF Cluster telecon is today:
> >
> > When: Tuesday Jan 31, 2pm ET / 11am PT
> > Dial: 877-668-4493
> > Access code: 23138379
> >
> > Agenda:
> > -HDF-EOS / CF Conversion Table
> > -Summer Meeting Technical Workshop showcasing CF-aware tools
> > -CF extensions desired at Level 1, Level 2, and Level 3
> > -Mapping to ontology
> >
> > http://wiki.esipfed.org/index.php/CF
> >
> >
> > ------------------------------------
> > Rob Raskin
> > Group Supervisor, Science Data Engineering and Archiving
> > Instrument Software and Science Data Systems Section
> > Jet Propulsion Laboratory
> > Pasadena, CA 91109
> > (818) 354-4228
> > _______________________________________________
> > Esip-cf mailing list
> > Esip-cf at lists.esipfed.org
> > http://www.lists.esipfed.org/mailman/listinfo/esip-cf
>
>
>
> ------------------------------
>
> Message: 2
> Date: Tue, 31 Jan 2012 16:31:37 -0700
> From: Russ Rew <russ at unidata.ucar.edu>
> To: Upendra Dadi <upendra.dadi at noaa.gov>
> Cc: esip-cf at lists.esipfed.org
> Subject: Re: [ESIP-CF] CF Cluster telecon today
> Message-ID: <10347.1328052697 at unidata.ucar.edu>
>
> > Hi All,
> > I added a link on the Wiki to a netCDF file created by NDBC which
> > uses groups.
> >
> > On a related note, I want to ask this group if they have considered
> > using user defined structures in place of groups. As you might be
> > knowing that netCDF-4 allows compound types which are based on C struct.
> > Compound types along with variable length arrays could often be a good
> > substitute for using groups. With regard to CF, incorporating groups, I
> > am guessing, is much more challenging than including compound types.
> > Anybody disagrees? I am looking for some examples where groups are much
> > better suited than using compound types and/or variable length arrays.
> > Please let me know if you have one. Thank you!
>
> Groups and compound types are intended for different purposes. A group
> is really just a name space or container for variables, dimensions,
> attributes, user-defined types, other groups, and data. So, for
> example, it would be possible to store data for separate geographic
> regions in distinct groups, in which the same names could be used for
> all the data objects, e.g.:
>
> http://www.unidata.ucar.edu/netcdf/workshops/2010/netcdf4/Groups.html
>
> Groups can be useful for factoring out other kinds of common information
> than geographic regions, e.g. shared metadata.
>
> Compound types, like structs in C and derived types in Fortran, are
> useful for specifying data that has named members, possibly of different
> types. For example
>
> netcdf odnc4 { // obs data in netCDF-4, inspired by example from Tom
> Kunicki
> types:
> compound observation_t {
> int time ;
> float temperature ;
> float pressure ;
> }; // observation_t
>
> compound observation_att_t {
> string time ;
> string temperature ;
> string pressure ;
> }; // observation_att_t
>
> dimensions: // these two unlimited dimensions are
> independent
> station = UNLIMITED ;
> observation = UNLIMITED ;
>
> variables:
> int station_id(station) ;
> station_id:standard_name = "station_id";
> float latitude(station) ;
> latitude:units = "degrees_north" ;
> float longitude(station) ;
> longitude:units = "degrees_east" ;
> float elevation(station) ;
> elevation:units = "feet" ;
> elevation:positive = "up" ;
> observation_t observations(station, observation) ;
> observations:coordinates =
> "observations.time longitude latitude elevation" ;
> observation_att_t observations:units =
> {"days since 1929-1-1 0:0:0", "degF", "hectopascal"} ;
> ...
>
> --Russ
>
> > Upendra
> >
> > On 1/31/2012 7:11 AM, Raskin, Rob (388M) wrote:
> > > This is a reminder that the rescheduled CF Cluster telecon is today:
> > >
> > > When: Tuesday Jan 31, 2pm ET / 11am PT
> > > Dial: 877-668-4493
> > > Access code: 23138379
> > >
> > > Agenda:
> > > -HDF-EOS / CF Conversion Table
> > > -Summer Meeting Technical Workshop showcasing CF-aware tools
> > > -CF extensions desired at Level 1, Level 2, and Level 3
> > > -Mapping to ontology
> > >
> > > http://wiki.esipfed.org/index.php/CF
> > >
> > >
> > > ------------------------------------
> > > Rob Raskin
> > > Group Supervisor, Science Data Engineering and Archiving
> > > Instrument Software and Science Data Systems Section
> > > Jet Propulsion Laboratory
> > > Pasadena, CA 91109
> > > (818) 354-4228
> > > _______________________________________________
> > > Esip-cf mailing list
> > > Esip-cf at lists.esipfed.org
> > > http://www.lists.esipfed.org/mailman/listinfo/esip-cf
> >
> > _______________________________________________
> > Esip-cf mailing list
> > Esip-cf at lists.esipfed.org
> > http://www.lists.esipfed.org/mailman/listinfo/esip-cf
>
>
> ------------------------------
>
> _______________________________________________
> Esip-cf mailing list
> Esip-cf at lists.esipfed.org
> http://www.lists.esipfed.org/mailman/listinfo/esip-cf
>
>
> End of Esip-cf Digest, Vol 5, Issue 1
> *************************************
>
--
==== Ted Habermann ===========================
Enterprise Data Systems Group Leader
NOAA, National Geophysical Data Center
V: 303.497.6472 F: 303.497.6513
"The people who are crazy enough to think
they can change the world, are the ones
who’ll do it" Apple
==== Ted.Habermann at noaa.gov ==================
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.lists.esipfed.org/pipermail/esip-cf/attachments/20120201/c067f544/attachment.html>
More information about the Esip-cf
mailing list