catalog schema question: variable element

[Ethan Davis]

Hi Darren,

Boy, I really blew it on this one. There is actually a fairly clean way 
to include human-readable descriptions of a variable. The <variable> 
element is defined as "mixed" which means you can put text in the 
content. It appears that this isn't documented very well (oops, we'll 
have to fix that) but we've been using it for some time. Here's an 
example from one of our GRIB datasets:

<variables vocabulary="GRIB-1">
  <variable name="Absolute_vorticity" vocabulary_name="Absolute vorticity" units="1/s" vocabulary_id="1,7,2,41">Absolute vorticity @ isobaric</variable>
  <variable name="Accumulated_snow" vocabulary_name="Accumulated snow" units="kg/m^2" vocabulary_id="1,7,2,65">Accumulated snow @ surface</variable>
  <variable name="Albedo" vocabulary_name="Albedo" units="%" vocabulary_id="1,7,2,84">Albedo @ surface</variable>
   ...
</variables>

That's probably the best solution for your situation.

Sorry for the round about way of getting here.

Ethan





Ethan Davis wrote:
> Hi Darren,
>
> Quite right, you certainly can have multiple <variables> elements.
>
> My mistake, I was misreading the schema.
>
> Sorry about that.
>
> Ethan
>
> Darren Hardy wrote:
>> Yes, I'm trying to write validate catalog.xml files that will work 
>> with THREDDS tools, but will also be a data source for a digital 
>> library system that we're using.
>>
>> I'm looking at the 1.0 schema but I don't see that restriction:
>>
>>   http://www.unidata.ucar.edu/schemas/thredds/InvCatalog.1.0.xsd
>>
>> To test, I grabbed a working catalog:
>>
>>   
>> http://motherlode.ucar.edu:8080/thredds/catalog/nexrad/level2/KVWX/20060809/catalog.xml 
>>
>>
>> Then, I added a second variables section, like so:
>>
>> <catalog 
>> xmlns="http://www.unidata.ucar.edu/namespaces/thredds/InvCatalog/v1.0"
>>     xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance'
>>     
>> xsi:schemaLocation="http://www.unidata.ucar.edu/namespaces/thredds/InvCatalog/v1.0 
>> http://www.unidata.ucar.edu/schemas/thredds/InvCatalog.1.0.xsd">
>>
>> ....
>>
>>       <variables vocabulary="DIF">
>>         <variable name="Reflectivity" vocabulary_name="EARTH SCIENCE 
>> &gt; Spectral/Engineering &gt; Radar &gt; Radar Reflectivity" 
>> units="db" />
>>         <variable name="Velocity" vocabulary_name="EARTH SCIENCE &gt; 
>> Spectral/Engineering &gt; Radar &gt; Doppler Velocity" units="m/s" />
>>         <variable name="SpectrumWidth" vocabulary_name="EARTH SCIENCE 
>> &gt; Spectral/Engineering &gt; Radar &gt; Doppler Spectrum Width" 
>> units="m/s" />
>>       </variables>
>>
>>       <variables vocabulary="human-readable">
>>         <variable name="foobar" vocabulary_name="blah blah blah" 
>> units="db" />
>>       </variables>
>>
>> ....
>> </catalog>
>>
>> and it passed a Xerces validation of it.
>>
>>
>>
>> -Darren
>>
>> -- 
>> Darren Hardy
>> Ph.D. Student
>> Bren School of Environmental Science & Management
>> University of California, Santa Barbara
>> dhardy at bren.ucsb.edu
>> www.bren.ucsb.edu/~dhardy
>>
>> On Aug 9, 2006, at 12:23 PM, Ethan Davis wrote:
>>
>>> Hi Darren,
>>>
>>> Darren Hardy wrote:
>>>> Ok, so I could use two <variables> elements to provide all these 
>>>> descriptions, like so:
>>>>
>>>> <variables vocabulary="CF-1.0">
>>>>    <variable name="SST" vocabulary_name="sea_surface_temperature" 
>>>> units="degC"/>
>>>>    <!-- Foobar omitted because it does not have a CF standard_name -->
>>>> </variables>
>>>>
>>>> <variables vocabulary="human-readable">
>>>>    <variable name="SST" vocabulary_name="OI Cloud-free SST, blah 
>>>> blah blah" units="degC"/>
>>>>    <variable name="Foobar" vocabulary_name="My foobar variable" 
>>>> units="m" />
>>>> </variables>
>>>>
>>>> It looks like the catalog schema provides for multiple variables 
>>>> elements, so this would work for me.
>>> Currently, the schema only allows one <variables> element per 
>>> dataset. The schema defines it like this
>>>
>>>      <xsd:element ref="variables"/>
>>>
>>> and the default for the minOccurs and maxOccurs attributes is one. 
>>> So, I don't think a catalog with a <dataset> element that had two 
>>> child <variables> elements would validate.
>>>
>>> How are you planning on your catalog being used? Are you trying to 
>>> feed this information into another system?
>>>
>>> Ethan
>>>
>>> --Ethan R. Davis                                Telephone: (303) 
>>> 497-8155
>>> Software Engineer                             Fax:       (303) 497-8690
>>> UCAR Unidata Program Center                   E-mail:    
>>> edavis at ucar.edu
>>> P.O. Box 3000
>>> Boulder, CO  80307-3000                       
>>> http://www.unidata.ucar.edu/
>>> --------------------------------------------------------------------------- 
>>>
>>>
>>>
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>>>
>>> To unsubscribe thredds, visit:
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>>>
>

-- 
Ethan R. Davis                                Telephone: (303) 497-8155
Software Engineer                             Fax:       (303) 497-8690
UCAR Unidata Program Center                   E-mail:    edavis at ucar.edu
P.O. Box 3000
Boulder, CO  80307-3000                       http://www.unidata.ucar.edu/
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