Vocabularies and VOEvent
norman at astro.gla.ac.uk
Mon Feb 4 15:00:56 PST 2008
On 2008 Feb 4, at 22:10, Roy Williams wrote:
> But I am still waiting for the cost benefit analysis.
Hang on: you asked for use-cases, you got use-cases. You want a cost-
* Benefit: you get the use-cases
* Cost: you have to put "voevent:" in front of your KISS keywords in
the VOEvent packet.
> I know very little about it except that precision of expression is
> possible (eg "I want Supernovae Ia but not Ic").
Precision (neigher too much nor too little) is the goal here.
> I worry that there are many vocabularies with no agreement.
The goal is multiple vocabularies, with just the right amount of
> I worry that there are many representation technologies for
> vocabularies that use complicated languages.
Nope, just SKOS.
I'm taking it that the application of all this to VOEvent will be to
have very slightly magic strings in the 'why' position. There are
some finicky technicalities about the best way to curate, version and
distribute these, and these are what are being discussed on the
semantics list. But these technicalities are all about how one makes
vocabularies robust no-brainers for the users, with the first
representative of 'the users' being the VOEvent standard authors, and
the subsequent developers who will use their standard.
> I worry that use of vocabularies will require knowledge of complex
> matters like namespaces,
> schema extension,
If you want to do funky things with VOEvents or archives of them, then
it might turn out that this would help, but it won't be necessary.
Perhaps a very little.
Definitely not (heh, unless you're Brian!)
> I worry about no being able to use SQL or even Xquery but must learn
> a new query language.
_In principle_ there's a slight complication in that the namespace
prefixes (why='voevent:supernova1a') are arbitrary (this is the same
issue that the Registry folk had to handle a few months ago). But if
you want to, you could specify VOEvent to mandate that the prefix
always be the same one (such as 'voevent:'), so the resulting string
will be constant, and so you can SQL away all you like without ever
having heard of SKOS. Of course, if you're restricting yourself to
dumb string-matching, then you can't get the added value that
supernova1a is a type of supernova.
> I worry that the creator of the VOEvent will also need to understand
> these complex technologies, meaning that few event streams will be
> done this way. Are any of these valid worries?
They are entirely valid worries. Fortunately, the answers to all of
them are easy.
> (*) http://www.astronomerstelegram.org/
> click on "Post a New Telegram", you see these categories:
> Request for Observations, A Comment, AGN, Asteroids, Binaries, Black
> Holes, Comets, Cosmic Rays, Cataclysmic Variables, Globular
> Clusters, Gamma-Ray Bursts, Meteors, Microlensing Events, Neutron
> Stars, Novae, Planets, Planets (minor), Pulsars, Quasars, Soft Gamma-
> ray Repeaters, Solar System Objects, The Sun, Supernovae, Supernova
> Remnants, Transients, Variables, Stars
Delete the spaces, prefix a suitable URL and a '#' and bingo!, you've
got your SKOS vocabulary. Job done! (attached)
Are you proposing this SKOS vocabulary for inclusion in the set of
distributed vocabularies? I could sling it in the repository just now.
All the best,
Norman Gray : http://nxg.me.uk
eurovotech.org : University of Leicester
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