Hi Reiner, Sorry to have taken so long to respond to your question: > I am making progress using netcdf4 on Linux and I am thinking of > implementing a cache mechanism to avoid retrieving the same data twice over > the Internet. I would like this cache to live-on between sessions and > accumulate all accessed data in all sessions connected to a given nc file. > Of course, the cache contents would have to be discarded when the nc file on > the server side changes. Now I am wondering whether a netCDF/OpenDAP client > has any way of retrieving version or file time stamp information of the > remote data set. Comments and suggestions are greatly appreciated. No sorry, I know no way of getting version or time stamp information unless it is part of the metadata or data in the file you are accessing. In general, there may not be a single file associated with the information returned from an OPeNDAP query. For example, if you request information from a TDS server via DAP protocols, the response may require opening and aggregating data and metadata from multiple files, which may span a wide range of times. Since OPeNDAP protocols are layered on top of HTTP, you may be able to use information in the HTTP header, but that's not available through the netCDF OPeNDAP client. For more information about this approach, see the DAP 2.0 standard, section 7.1.4, "Support for HTTP/1.1 caching": http://opendap.org/pdf/ESE-RFC-004v1.1.pdf There may be something more up-to-date on OPeNDAP support for caching, but I'm not aware of it. I'm Cc:ing Dennis Heimbigner, the Unidata expert on OPeNDAP client and server protocols. He can correct any misstatements I've made and may have more to add about how you could tackle this problem. --Russ Russ Rew UCAR Unidata Program address@hidden http://www.unidata.ucar.edu Ticket Details =================== Ticket ID: VIG-404579 Department: Support netCDF Priority: High Status: Closed
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