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Hi, Ata (ATAE@xxxxxxxxxxxxxxxxxxxxxxxxxxx) writes: > ... By a Domain I mean some kind of tagging in netCDF to indicate > that the data is applicable to a particular domain (eg CAD. Vision, > Time-series, etc..). My routines for analysing time-series are not able to > take advantage of data in a form suitable for CAD/CAM, or images or > etc.. If there was such a tag, applications could automatically decide > whether the data in a netCDF file is relevant to them. This would allow a > more object oriented approach and save on development time for > applications. ... Coincidentally, I was just about to announce an implementation of a very similar idea to Ata's proposed Domains that has grown out of an email discussion with Nancy Soreide, Rich Signell, Donald Denbo, and others. The idea is to support the registry of sets of conventions for netCDF files, and to permit a hierarchy of conventions that can support an object-oriented approach to discipline-specific netCDF conventions. We have set up an ftp directory, pub/netcdf/Conventions on ftp.unidata.ucar.edu, where outside individuals or groups will be able to create directories and write files. This directory is a repository for registered sets of netCDF conventions, as supported by the global Conventions attribute to be described in the Attribute Conventions section of the netCDF User's Guide. Gopher access to these conventions is also supported through the Unidata gopher server. The reason it has taken us so long to implement this is that we were trying to solve some problems with uploading files in the FTP server we're using, but we have an interim workaround that should permit outside users to upload and change conventions documents without making our FTP archives world-writable. The documentation update for the Conventions attribute will be included in the next (minor) release, netCDF version 2.3.3. Description of the Conventions Attribute ======================================= If present in a netCDF file, `Conventions' is a global attribute that is a character array for the name of the conventions followed by the file, in the form of a string that is interpreted as a directory name relative to directory: pub/netcdf/Conventions on host: ftp.unidata.ucar.edu This permits a hierarchical structure for conventions and provides a place where descriptions and examples of the conventions may be maintained by the defining institutions and groups. For example, if a group named NUWG agrees upon a set of conventions for dimension names, variable names, required attributes, and netCDF representations for certain discipline-specific data structures, they may store a document describing the agreed-upon conventions in a file in the NUWG/ subdirectory of the Conventions directory, and files that followed these conventions would contain the global attribute :Conventions = "NUWG"; Later, if the group agrees upon some additional conventions for a specific subset of NUWG data, for example time series data, the description of the additional conventions might be stored in the NUWG/Time_series/ subdirectory, and files that adhered to these additional conventions would use the global attribute :Conventions = "NUWG/Time_series"; Here are some other examples of plausible values for a Conventions attribute: :Conventions = "WHOI/Time_Series"; // WHOI's version :Conventions = "WHOI/Time_Series/Version_3"; // later extensions :Conventions = "PMEL-EPIC/CTD"; // this is a PMEL-EPIC CTD file Typical contents of a conventions directory will be one or more conventions documents in some form agreed upon by the community that supports the conventions and one or more CDL files that provide examples of netCDF file structures that follow the conventions. Unidata makes available a limited amount of disk space for anonymous FTP access for these convention documents and provides mechanisms for outside groups to create and maintain their own convention hierarchies. Unidata does not endorse or maintain any conventions provided by outside groups. ________________________________________________________________________ Russ Rew Unidata Program Center russ@xxxxxxxxxxxxxxxx UCAR, PO Box 3000 Boulder, CO 80307-3000
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