VOEvent Update

[Roy Williams]

Hi Pierre and Tim

I understand that you would like to represent the orbit/ephemeris of *moving* objects as part of the VOEvent packet. Rather than working the way VOEvent was designed -- with typed Groups of Params and Tables -- you propose to build an XML schema extension for this purpose, using all or part of the STC schema. This would then be linked in somehow -- in a way that we found really too difficult in the past.

My worry is that parsers that have been built to read "off-the-shelf" VOEvent 2.0 would not be able to parse this enhanced version of VOEvent, and thus we would fail in our mission of interoperability. Another problem would happen when other groups are required to build their own extension schemas for their purposes, and are turned away, first by the technical task, and then by the requirement to have IVOA approval for the extension.

Perhaps you can help me understand how the LIGO-Virgo VOEvents would be built using extension schemas? See below. Neither the existing WhereWhen schema, nor the STC schema shows how to represent a *probability density* on the sky, which is the LIGO-Virgo statement of where to find the source. How should this be recast in your suggested mechanism of schema extension?

Roy
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LIGO document
"VOEvent Documentation: How to read and interpret a VOEvent"
https://gw-astronomy.org/wiki/pub/LV_EM/TechInfo/VOEvent_Documentation.pdf

This excerpt from the above paper shows how a typed Group is used by LIGO-Virgo to communicate a probabilistic skymap:

<Group type="GW_SKYMAP" name="BAYESTAR">
  <Param name=" skymap_png_x509 " value="https://gracedb.ligo.org/api/events/G96195/files/skymap.png,0" ucd="meta.ref.url">
    <Description>Sky Map image X509 protected</ Description>
  </Param>
  <Param name="skymap_fits_x509" value="https://gracedb.ligo.org/api/events/G96195/files/skymap.fits.gz,0" ucd="meta.ref.url">
    <Description>Sky Map FITS X509 protected</Description>
  </Param>
  <Param name="skymap_png_shib" value="https://gracedb.ligo.org/events/G96195/files/skymap.png,0" ucd="meta.ref.url">
    <Description>Sky Map image Shibboleth protected</Description>
  </Param>
  <Param name="skymap_fits_shib" value="https://gracedb.ligo.org/events/G96195/files/skymap.fits.gz,0" ucd="meta.ref.url">
    <Description>Sky Map FITS Shibboleth protected</Description>
  </Param>
</Group>