VOEvent References

[Frederic V. Hessman]

Roy's low-level solution is fine as a VOEvent hack, but an equally  
practical solution with the possibility of maintaining generality  
RIGHT NOW is

<Reference type="ivoat:lightCurve" ucd="meta.code.url" uri="http://nesssi.cacr.caltech.edu/catalina/20110314/1103141070764142069p.html 
">
	Light curve for the alert.
</Reference>

for which you simply have to check the type to understand very well.    
Roy's example means knowing that the name "Light curve chart" is what  
to look for, whereas looking for "ivoat:lightCurve" is just as easy  
and perfectly general.  There are a very small number of vocabularies  
which one could be looking for (here the IVOAT which, while not yet  
official, DOES exist: see http://www.astro.physik.uni-goettingen.de/~hessman/rdf/IVOAT/dict/L.html 
  and look for lightCurve).

I have added (or? haven't checked the new VOEvent schema) the ucd  
attribute for VO-compatibility.  This could be the way to make the  
"mime-sh" typing, e.g. by being able to use

	meta.code.xml
	meta.code.rtml
	meta.code.fits

but the other, better solution would be to be able to access

	type="ivoat:RTML"
	type="ivoat:FITSimage"
	...

so that there is just one, simple, uniform means of identifying  
content.  Roy's solution uses two XML constructs, 10 things to parse  
and 195 characters, mine one XML construct, 8 things to parse, and 174  
characters (well, one does nominally need a reference to the IVOAT  
namespace, but I'm sure Roy could hard-wire this one).   ;-)

Of course, as soon as I get a little bit of input, we can have a  
VOEvent vocabulary covering everything Roy could possibly dream of  
needing in as compact a set of terms as possible.

Rick

On 15 Mar 2011, at 22:29, Roy Williams wrote:

> Mike
> I should probably not talk any more about <Reference>, since my work  
> does not use it. Instead, there is another way to indicate URL links  
> in a VOEvent, specifically as a Param, for example:
>
> <Param name="Light curve chart" ucd="meta.code.url"
> value="http://nesssi.cacr.caltech.edu/catalina/20110314/1103141070764142069p.html 
> ">
>    <Description>Light curve for the alert</Description>
> </Param>
>
> The point here is that the author and subscriber can understand the  
> meaning from the *stream* metadata, figure out response, well in  
> advance of the arrival of the first event. Then *every* event of the  
> stream will have this same semantics.
>
> Whereas the Reference name and type is unconstrained and not seen  
> until the event arrives. I have no idea how to make code that can  
> respond effectively to an arbitrary <Reference>.
> Roy
>