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Hi, Here's the paper on the Unidata-centric view of the netCDF/HDF5 project that will be presented at the 84th Annual Meeting of the American Meteorological Society that will be held 11-15 January, 2004, at the Washington State Convention and Trade Center in Seattle, as part of the 20th International Conference on Interactive Information and Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology: http://my.unidata.ucar.edu/content/publications/2004AMS/rew_hartnett.pdf I'm currently putting together a quarterly review and a presentation for the 6-month Interim Review of the project to be held on Wednesday, 1:30pm to 3:00pm Mountain Time, by teleconference. If you have any milestones you want to mention or include, please let me know. Thanks! --Russ >From owner-netcdf-hdf@xxxxxxxxxxxxxxxx 10 2003 Nov -0700 18:40:07 Message-ID: <wrxekwf3cp4.fsf@xxxxxxxxxxxxxxxxxxxxxxx> Date: 10 Nov 2003 18:40:07 -0700 From: Ed Hartnett <ed@xxxxxxxxxxxxxxxx> In-Reply-To: <18.104.22.168.2.20031110141448.02b0ff68@xxxxxxxxxxxxxxxxx> To: Mike Folk <mfolk@xxxxxxxxxxxxx> Subject: Re: zero length attrributes... Received: (from majordo@localhost) by unidata.ucar.edu (UCAR/Unidata) id hAB1eAx3029513 for netcdf-hdf-out; Mon, 10 Nov 2003 18:40:10 -0700 (MST) Received: from rodney.unidata.ucar.edu (rodney.unidata.ucar.edu [22.214.171.124]) by unidata.ucar.edu (UCAR/Unidata) with ESMTP id hAB1e8Ob029504; Mon, 10 Nov 2003 18:40:08 -0700 (MST) Organization: UCAR/Unidata Keywords: 200311110140.hAB1e8Ob029504 Cc: netcdf-hdf@xxxxxxxxxxxxxxxx References: <wrxwua8qczz.fsf@xxxxxxxxxxxxxxxxxxxxxxx> <126.96.36.199.2.20031110141448.02b0ff68@xxxxxxxxxxxxxxxxx> Lines: 27 User-Agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.2 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: owner-netcdf-hdf@xxxxxxxxxxxxxxxx Precedence: bulk Mike Folk <mfolk@xxxxxxxxxxxxx> writes: > Ed, > Is a zero-length attribute in netCDF the same as a scalar, or is it > more like an empty array? I can't imagine a use for the latter, but > if it's needed it's needed. > It's more like an empty array, since a scalar would have one value to read/write, and an empty attribute has zero bytes to read and write. Of course if this was extremely difficult we could ask how much we really need it. Right now, it's "needed" in the sense that we have a requirement to support existing netcdf programs with a recompile, and they might be using zero length attributes. If there's an easy/elegant way to fake it, I'm certainly open to suggestions. I can't think of anything at the moment except to have a table of attribute names and lengths. We could store a zero in such a table, and store a byte of garbage in the actual attribute. The table entry could tell me that this attribute has length zero. But let's face it, that would be pretty cheesy! It would be a lot nicer all around if HDF5 allowed zero length attributes, if it's really easy for you to do so. Ed