[Voevent-core] Fwd: standard vocabulary

[Tony Linde]

I've always seen UCDs as like data types. They are applied to columns and
describe what type of data is in the column - so they are data types. Much
the same as 'float', which I guess you could call number.float;32bit if you
wanted to introduce more semantic structure into the name or just float if
not.

In which case GRB is not really relevant as a UCD, nor is
process.variation.burst;em.X-ray. As Rob says:
> But "GRBness" is not a scalar with some floating point value 
> attached, it is itself a state to be named.

So unless UCDs are now going to be turned into the new astro thesaurus or a
type of astro ontology, it doesn't seem to make sense to have a UCD for
GRBs.

T.

> -----Original Message-----
> From: owner-semantics at eso.org 
> [mailto:owner-semantics at eso.org] On Behalf Of Rob Seaman
> Sent: 17 May 2006 09:45
> To: Francois Ochsenbein
> Cc: Roy Williams; semantics at ivoa.net; voevent-core at us-vo.org> List
> Subject: Re: [Voevent-core] Fwd: standard vocabulary 
> 
> Hi Francois,
> 
> > In my mind, it's (hopefully) more than just flexibility -- it is a 
> > description of the phenomenon. Assigning a name to it does not 
> > describe it -- you could name it 054321ff instead of GRB and the 
> > semantic contents would be the same...
> 
> I think you have put your finger on it.  First, note that I 
> was not questioning the good work that has gone into UCDs for 
> their original purpose.  In the case of describing a keyword 
> or a column of a table, the point is that the column already 
> has a name attached, whether it is "RA" or "EXPOSURE" or 
> whatever.  The UCD in this case is providing additional 
> context to understand that "MAG_V" and "V_MAGNITUDE" are both 
> expressions of a quantity representing "phot.mag;em.opt.V".  
> The UCD unites the disparate quantities into a single 
> semantically manageable notion.
> 
> But "GRBness" is not a scalar with some floating point value 
> attached, it is itself a state to be named.
> 
> > The "atoms" used in
> > "process.variation.burst;em.X-ray" have all a definition in the UCD 
> > dictionary, their association therefore means something.
> 
> But what they mean is not intrinsic to the astronomy.  The 
> definition is not fixed in advance - it is the point of the 
> whole exercise.  A GRB or AGN or SN is a complex 
> object/process with many faces that depend on how it is 
> observed and from what preferred direction.  A GRB (or a 
> class of same) may result in several distinct phenomena that 
> astronomers are seeking to understand and unite into a single 
> coherent entity.  The atoms in this case are dividing the 
> science, rather than uniting it.
> 
> > Of course it would be possible to add "GRB" among the 
> atoms, but then 
> > you remove the possible relationship between e.g. GRB and 
> X-ray burst.
> 
> But that is purely a phenomenological relationship, whereas 
> there are many actual relationships of cause and effect 
> through complex physics that these UCD-like expressions do 
> nothing to address.  A supernova (of a particular type) is 
> the result of a binary star system exchanging mass that 
> eventually triggers TNR.  A nova is some other binary star 
> system whose mass exchange triggers only surface  
> burning.  There are similarities - and there are differences.   
> Additionally, the notion of evolution is missing - one class 
> of object may become another class of object.  I wouldn't 
> expect UCDs to help much here, but they shouldn't hinder by 
> implying that a GRB "is"  
> a "process.variation.burst; em.gamma".
> 
> Which is to say that an gamma-ray burst observed by Swift is 
> used to infer the existence of something we call a "GRB" 
> which exhibits many other observable aspects.  On the other 
> hand, the UCD "process.variation.burst; em.gamma" explicitly 
> misses those more physical implications.
> 
> > In other terms, the UCD is a way to describe phenomenae, 
> observables, 
> > parameters, etc... with a restricted set of well-defined "words".
> 
> Will agree with parameters and possibly observables.  Don't 
> think that we've capture "phenomena" yet.  In the latter 
> case, the vocabulary comes after the fact, not before.
> 
> Rob
> 
>