[Esip-documentation] ACDD 2-3 question (geospatiotemporal extent)

[Steve Hankin via Esip-documentation]

On 5/21/2014 12:20 PM, John Graybeal via Esip-documentation wrote:
> Hi Anna,
>
> As a significant driver I'll offer one opinion. Caveat emptor.
>> 1. Is this the best version to be using? (They will NOT be using groups)
> Arguably, yes it is the best version to be using, but it is not 
> approved at this point. I would say the status is 'stalled in a mostly 
> happy place' -- with one exception, I haven't heard any complaints 
> about this current 'Working' draft, which has been around for many 
> months now and has been carefully reviewed by at least one person.  I 
> *think* that all that is required for approval is for Derrick Snowden 
> (or someone he designates, ideally not the principle updater, hint 
> hint) to call a discussion/next steps meeting, at which any remaining 
> issues can be raised and resolved.
>
> There is only one open issue under discussion, namely *whether the 
> adoption of summary metadata for geospatiotemporal ranges is good, 
> tolerable, or bad*. It is hard to know for sure whether that will be 
> changed (I suspect it will not, just from comments so far). It is my 
> hope that the fact all these attributes are **recommended**, not 
> *required*, means that it will be acceptable to leave this material 
> in, perhaps with precautionary language (a proposal for which has 
> already been added).  We haven't had a discussion in the group yet 
> about this topic.
>

Hi John,

The draft at 
http://wiki.esipfed.org/index.php/Attribute_Convention_for_Data_Discovery_%28ACDD%29_Working 
needs only minor editorial additions to address the open issue discussed 
above.  In the ACDD document the word "Recommended" alone does not make 
users aware of the conditions under which the geospatiotemporal  extent 
attributes may lead to internally contradictory file content.   Here is 
a suggested addition:

      under "*Alignment with NetCDF and CF Conventions*" add ...

        Note that the geospatial and temporal extent of a CF dataset is
        self-documenting through its CF coordinate variables.  The
        intent of the ACDD geospatiotemporal extent attributes is to
        make it easier to infer this information from a file.  Since
        these attributes provide redundant information, they may create
        a risk of corrupted content.  The risk is highest for the time
        extents of files that are likely to be aggregated into longer
        time series, such as files output by numerical forecast models
        and in gridded satellite data products.


    under *Recommended Global Attributes: time_coverage_start,
    time_coverage_end, and time_coverage_duration* add ...

        please see note in the "Alignment with NetCDF and CF
        Conventions" section of this users guide

This does not change the content or spirit of the ACDD document.  It 
merely informs users of trade-offs that they should be aware of.

     - Steve

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