This report describes some existing facilities on the WWW that do some of the tasks expected of the VO.
CDS provide Simbad, Vizier, Aladin and a bibliographic archive. As with much of the CDS product, these services are interwoven and it's hard to see which part does what. Apparently:
NASA/IPAC provides NED. I quote from the introduction on the NED web-site: "It is built around a master list of extra-galactic objects for which cross-identifications of names have been established, accurate positions and redshifts entered to the extent possible, and some basic data collected. Bibliographic references relevant to individual objects have been compiled, and abstracts of extra-galactic interest are kept on line. Detailed and referenced photometry, position, and redshift data, have been taken from large compilations and from the literature. NED also includes images for over 700,000 extra-galactic objects from 2MASS, from the literature, and from the Digitized Sky Survey. NED's data and references are being continually updated, with revised versions being put on-line every 2-3 months."
In order to find out what these services can do, I tried to use them to do the Astrogrid use cases. I didn't have much success. The section names in the following are the Wiki-names of the use cases in the VO Wiki-web.
Vizier and Simbad can do the main flow of this use case, using Aladin as the display tool. Ironically, Aladin itself can't make the necessary selection. None of these tools can merge the tables of results.
NED can do some of this work. It can't select on radius from the search centre, but it can select on ranges of RA and dec., which is almost as good. It understands "QSOs" and "QSO clusters" as selection criteria. The plotter ("skyplot") from NED is poor (line graphics only) and is non-interactive: there is no way to select objects on the display and get to their details from the catalogue.
This feature is available in Simbad. Results of searches carry hyperlinks to entries in CDS' bibliographic service. However, only selected references are shown (to explain where the Simbad data came from, not to refer to the science). It is possible to query the bibliographic service directly, but the number of references returned is surprisingly small (e.g. 7 for a search on NGC1068).
NED allows one to query the database of abstracts directly by object name. This finds many (all?) references (e.g. 1249 for NGC1068).
I can't see a way to get any actual spectral pixel-data from any of these systems except one small part of IPAC. The SWAS mission, available through IPAC, serves spectra as either web graphics or in FITS files.
None of the systems seem to allow an instrument footprint as a search area in a query.
Aladin allows a use to draw one of a set of limited footprints as an overlay on an existing plot. If one then measures the footprint in Aladin one can get a search radius that encloses the footprint, and can search on that radius in Vizier. This allows the work to be done manually.
None of the systems do this use case. There are no links to observation-proposal systems.
As far as I can see, none of the systems cover this case. I haven't found any references to software for interconverting magnitudes and fluxes except in NED, which is trying to go in the opposite direction, from photometry to coarse spectra.
None of the systems even attempt this except for 2MASS (accessed through IPAC) which has a batch system for producing image extracts.
None of the systems can do these cases as written. There is no support for actually doing the astrometric fit, nor for plotting the residuals on the fit.
Vizier and Simbad can do most of SelectAstrometricStandards, but they cannot select the "best" catalogue out of the many available. Aladin doesn't help with this case, since the idea is to automate the process, not to do it interactively.
NED isn't very helpful, since stars are needed, not extra-galactic objects.
NED can do this very nicely, but only for one object at a time. The initial selection of data is not quite as general as in the use case. The plot is done as a web graphic displayed in a web browser.
Simbad, Vizier and Aladin can't do this work. It isn't even straight-forward to extract the photometry so that one can do it manually.
None of the systems allow this work to be done as stated.
NED allows references to be looked up, but not using bibcodes.
Vizier, Simbad and Aladin do not support bibcodes as a search term, but they do return bibcodes in the results of their results. The CDS bibliographic service does good searches by bibcodes.
None of the software helps with handling the list of data and bibcodes as suggested in the use case. Aladin could be used to display the objects in the user's catalogue and the user could then cross them off as the bibcodes were checked by drawing into the graphics overlay.
As far as I can see, none of the systems inspected here deal with these issues.
Some of the systems look very much like "the VO", especially Vizier and the fancier bits of NED. However, all the systems have the same basic philosophy: "display lots of data and metadata in a web page and give chains of hyperlinks to even more data." This is all one can do easily with the existing infrastructure, but it isn't "the VO".
Most of the use cases weren't supported because they involved the technique "do a search, then do something specific with the results of the search". The VO-like archives aren't set up to handle the "do something with the results" part, since they only represent the results as web-pages, not as semantically-useful data held for further processing. The exception is the making of synthetic spectra in NED, and this is a specific application - a vertical integration - that's clearly been coded in specially. It's not the kind of processing that a user can set up using a script and separate services at NED.
Some of the use-cases failed because the various archive don't have uniform criteria for selecting objects. In any given query, the selection criteria must either be on quantities that the interface designer coded into the UI, or there must be a free-form interface for specifying other criteria: a query language known to the user. The existing systems don't expose a query language, and their web interfaces only deal with a few quantities.
The use case GetReducedSpectra fails because the systems don't seem to provide reduced spectra. They only deal in images and tables.
The systems don't seem to deal in identified usage. Presumably, this means that they allow less access to data than a given user is entitled to.
In general, the systems reviewed let you look up more easily data that you could get by trawling through paper journals or by using interfaces to individual large archives. They require you either to know what you are looking for at the start (e.g. which catalogues to search) or to be prepared to spend a long time browsing. The output of the search is as for searches in paper collections: text you can read, but not machine-readable data products.
This begs the question: how much of what the VO ought to do is just a better version of this automated paper-searching?