IVOA VOTable signature issue

[Pierre Fernique]

Dear DAL and App contributors,
and especially SIAv2 and Datalink authors,

In the contexte of the Aladin v10 developments, we are facing to a 
recurrent issue in the IVOA protocol suite.

*Most of IVOA protocols return VOTable, but without any signature or 
magic code. *
The consequence: IVOA clients can not easily recognize that this VOTable 
stream comes from a CS, a SIAv1, a SIAv2, a SSA, a Datalink, a TAP, an 
obsTAP or any other IVOA VOTable query result.

Based on the presence of some UCDs or utypes or INFO tags, Aladin tries 
to recognize the original protocol in order to have the adequat actions 
(basic table display, fov supports, popup menus, column display 
filtering...). But we fail to find such a method for SIAv2. We are, more 
or less able to recognize obsCore results (based on utypes list =>  
"obscore:ObsDataset.dataProductType", "obscore:Access.Reference" and 
"obscore:Access.Format" , but it is not specifical to SIAv2.

We are facing to the same difficulty for Datalink results. In this case, 
it is worse in the sense that some providers have already inserted 
Datalink links inside SIAv1 or CS results (see examples below). So in 
these cases,*we cannot know "a priori" that such link will return 
Datalink VOTable stream*. Without this knowledge, at the end, Aladin can 
only try to display on the sky view the VOTable Datalink result as a 
regular astronomical catalog (sad !).

So, how can we do ? Thanks for any help.

*For the future standard releases, may we just think to systematically 
add the standardID of the original protocol inside an INFO tag, or 
something equivalent ?*

Pierre Fernique & Chaitra (in charge of SIAv2/Datalink/... 
implementation in Aladin v10)

---

Datalink examples:

*GAVO SIAv1*

  * http://dc.zah.uni-heidelberg.de/lswscans/res/positions/siap/siap.xml?POS=210.8431667,54.2961666667&SIZE=0.1323&FORMAT=image/fits
  * => Example of Datalink URL inside the result :
    http://dc.zah.uni-heidelberg.de/lswscans/res/positions/dl/dlmeta?ID=ivo%3A//org.gavo.dc/%7E%3Flswscans/data/part2/Schmidtplatten/FITS/A82.fits

*VizieR CS*

  * http://vizier.u-strasbg.fr/viz-bin/votable?-source=B%2Fcfht%2Fobscore&-c=09+55+33.17+%2B69+03+55.1&-out.add=_RAJ,_DEJ&-oc.form=dm&-out.meta=DhuL&-out.max=999999&-c.rm=10.81&-out=_VizieR,*Mime(image/fits),*&-mime=TSV&-out.all
  * => Example of Datalink URL inside the result :
    http://www.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/caom2ops/datalink?runid=ejkaxv927qnvu4ef&ID=caom%3ACFHT%2F469601%2F469601o

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