Issue in SODA standard: BAND param max values

[alberto micol]

The SODA v1.0, in paragraph 4.2  "SODA Service Descriptor from DataLink" 
expresses the maximum BAND interval in this way: 
  <PARAM name="BAND" unit="m" ucd="em.wl;stat.interval"
    datatype="double" arraysize="2"      
    xtype="interval" value="">     
    <DESCRIPTION>The wavelength intervals to be extracted</DESCRIPTION>
    <VALUES>                                                           
      <MIN value="3e-7"/>
      <MAX value="8e-7"/>
    </VALUE>             
  </PARAM>  

The Issue

That is wrong, because the value attributes in the MIN and MAX elements are spelt as if the PARAM were of arraysize=“1”.

Indeed astropy gives a warning on that; try this:

import pyvo
datalink_url = 'http://archive.eso.org/datalink/links?ID=ivo://eso.org/ID?ADP.2016-11-17T12:51:01.877’
datalink = pyvo.dal.adhoc.DatalinkResults.from_result_url(datalink_url)

and you will get (until we fix our datalink)

WARNING: E02: ?:?:?: E02: Incorrect number of elements in array. Expected multiple of 2, got 1 [astropy.io.votable.converters]


I think the solution is:

The PARAM expresses an interval, and as such the only possible way to describe its limits is by stating:
    <VALUES>                                                           
      <MAX value=“3e-7 8e-7"/>
    </VALUE>             
similarly to what is already done for the CIRCLE and other non scalar params.
(When I do that, astropy is happy)

I’m going to have our datalink changed accordingly, as I prefer not to have astropy complaining.
(you will notice when the example above will not throw any warning)
 
All the very best to all,
Alberto


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