Server-side Operations for Data Access version 1.0 Proposed Erratum 3: Ambiguous text and wrong VOTable syntax in BAND example

Author: François Bonnarel

Date last changed: 2023-01-23

Date accepted:2023-07-26

Rationale

In section 4.2, the VOTable excerpt given for the BAND PARAM is somewhat ambiguous for the MIN and MAX elements syntax. The values of these elements are single doubles while the BAND arraysize attribute is 2. It has to be clarified that the MIN single value applies to the two elements in the BAND array as well as the MAX single value. This is consistent with a generic rule for MIN/MAX values for array-valued PARAMs and FIELDS as described in the VOTable specification starting from version 1.5. PARAMs and FIELDs with "interval" xtype do not apply a specific rule for MIN/MAX interpretration.

In addition the closing tag of the VALUES element is wrongly written

/VALUE

instead of

/VALUES

This ambiguity orignally described on github in SODA issue #2 (https://github.com/ivoa-std/SODA/issues/2)

Erratum Content

This Erratum proposes following changes.

Modify text and fix VOTable syntax

In §4.2 "*SODA Service Descriptor from DataLink*" of SODA-1.0, update the BAND text and example in

from

For float-valued intervals (e.g., the standard BAND and TIME parameters), \xmlel{VALUES/MIN} and \xmlel{VALUES/MAX} should be used to communicate the range
of values for which clients can expect to receive data. Example:
<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>  

to

For float-valued intervals (e.g., the standard BAND and TIME parameters), \xmlel{VALUES/MIN} and \xmlel{VALUES/MAX} are single values
 which apply to  the two elements in the BAND array, as stated in the VOTable specification starting from version 1.5, and in the DALI specification starting from version 1.2. 
There is no specific rule to apply for parameters with xtype=interval.  Example:
<PARAM name="BAND" unit="m" ucd="em.wl;stat.interval"
    datatype="double" arraysize="2"      
    xtype="interval" value="">     
    <DESCRIPTION>The wavelength intervals to be extracted. MIN (resp. MAX) is the minimal (reps. maximal) value of the two bounds of the interval</DESCRIPTION>
    <VALUES>                                                           
      <MIN value="3e-7"/>
      <MAX value="8e-7"/>
    </VALUES>             
  </PARAM>  

Impact Assessment

Making the text less ambiguous will help implementers to deliver correct values of MIN/MAX elements for intervals. Fixing the VOTable syntax in an example will make no harm to any service and will avoid implementers writing code delivering incorrect VOTables.