Suppose you have a couple of positions for “interesting” objects. Can we find spectra for them?
SSAP is the traditional VO protocol to access spectra, quite like SIAP, and we could query SSAP services just like we queried SIAP services. However, SSAP only lets you access one object at a time, which is kind of tedious.
Let’s use
ObsTAP = TAP with table ivoa.obscore
ivoa.obscore has lots of metadata on observational data products (spectra, cubes, timeseries).
Having what people generally call a “data model” – here, rather a set of pre-defined columns – enables a lot of powerful data discovery scenarious when coupled with TAP. So, why do we bother with SCS, SIAP, and SSAP?
Good question. It mainly has historical reasons – S*AP where easier to define than TAP and Obscore. And until datalink was there, there were a few tricks you could play with them that just don’t work with simple ObsTAP (cutouts, for instance).
Even now, there’s still much less data in ObsCore services than in SSAP; hence, if your problem easily admits querying through SSAP, it’s certainly no mistake to do so, perhaps in addition to Obscore (beware: there is some data that’s in Obscore but not in SSAP).
Plan: