Object Visibility Simple Access Protocol Semantic Problem

[Gilles Duvert]

Dears,

The Object Visibility Simple Access Protocol <http://ivoa.net/documents/ObjVisSAP/index.html> WD uses the term "visibility" in the general acceptance, "being visible".
However, "visibility" is unfortunately widely used in the interferometric community for (in short) naming the value of the fringe contrast. As such, "visibility" data are exposed and queried in the VO---that have nothing to do with OVSAP topic.

When both concepts are present, such as in the VO tool Aspro <http://www.jmmc.fr/aspro_page.htm>, interferometric visibilities are "visibilities" and the concept of an object  "visible" above the horizon of a given observatory/telescope/interferometer is 
termed "observability", so Aspro can happily plot "observability tracks" atop a "visibility" map.
Worse, "Object Visibility" is also widely used in the literature as refering to the interferometric fringe contrast of an (astronomical) object.
On the other hand, the p2web <https://www.eso.org/sci/observing/phase2/p2intro.html> ESO tool refers to a "Target Visibility" with the same meaning as in OVSAP. "Target" is precise in the context of a facility, "Object" is the science counterpart of the 
target.

This semantic clash was reported as an issue during last week's Interop. May I suggest, since this very useful WD is now reaching version 1.0, to circumvent any potential problem by being more precise, e.g., avoiding the use of the terms "visibility" and 
"object visibility", in favor of the compound "Target Visibility" ?

Of course interferometry-related normalizing documents should somehow become aware of the synonym, this is another story.:-)

Kind Regards,
Gilles Duvert




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