SSA-1_1-Err-4 < IVOA

---+ SSA v1.1 Erratum 4: Make coverage optional

Author: James Dempsey

Date last changed: 2023-12-04

Date accepted:

Github Issue: [[https://github.com/ivoa-std/SSA/issues/8][SSA Issue #8]]

---++ <a name="Rationale"></a>Rationale

SSA 1.1 sec 4.2.5.10 states MANdatory coverage information (!Char.SpatialAxis.Coverage.Location.Value + 2 others), but they are missing from the example in Appendix A. Theoretical services cannot provide coverage information so these columns should be made optional to support theoretical services.

---++ <a name="Erratum_Content"></a>Erratum Content

*In section 4.2.5.10*, add the following text at the end of the introductory sentence.

<blockquote>
This component is optional to support theoretical services which do not
have coverage information. However, where coverage information is
available, such as in observational services, the columns
!Char.SpatialAxis.Coverage.Location.Value,
!Char.SpatialAxis.Coverage.Bounds.Extent,
!Char.TimeAxis.Coverage.Location.Value,
!Char.SpectralAxis.Coverage.Location.Value, and !Char.SpectralAxis.Coverage.Bounds.Extent should be provided.
</blockquote>

and in the table in that section change the value in the Req column from MAN to REC for the following rows:

| UTYPE | Description | Req | Default |
| !Char.SpatialAxis.Coverage.Location.Value | Observed position, e.g., RA DEC | *REC* | |
| !Char.SpatialAxis.Coverage.Bounds.Extent | Aperture angular diameter, deg | *REC* | |
| !Char.TimeAxis.Coverage.Location.Value | Midpoint of exposure (MJD) | *REC* | |
| !Char.SpectralAxis.Coverage.Location.Value | Midpoint of Spectral coord range | *REC* | |
| !Char.SpectralAxis.Coverage.Bounds.Extent | Width of spectrum in meters | *REC* | |

---++ <a name="Impact_Assessment"></a>Impact Assessment

By loosening the requirements for positional description of the spectra,
existing theory services will be able to be compliant. Clients will need
to allow for the coverage fields to be missing.  However, they already
need to do that for established SSA theory services, of which there are
at least five at this point; !RegTAP query:

<pre>select count(ivoid)
from rr.res_detail
where detail_xpath='/capability/dataSource'
and detail_value like 'theor%'
</pre>

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Topic revision: r2 - 2023-12-06 - MarkusDemleitner