2-stage identifier resolution

[Roy Williams]

Dear Registry Group

I am in the midst of writing about VOEvents, and I found myself 
producing the material below, which concerns IVO identifiers, and how 
to use the Registry to resolve them. Basically, what it says is that if 
the identifier has a # symbol in it, then resolution is a two-stage 
process: first invoke any Registry to find out which VOEvent repository 
to invoke. But if there is no # symbol, then it can be done in one 
call.

Is this correct?
Roy



For these reasons, VOEvent packets will often contain VO identifiers, 
as defined and discussed in [16]. These take the general form 
"ivo://authorityID/resourceID#localID", and are references to metadata 
packets that may be found at a VO registry or VOEvent database. When 
such an identifier is resolved, it means that the VOEvent metadata 
packet is obtained in exchange for the identifier. Such resolution 
happens through the global, distributed IVOA registry in two stages: 
first use any VO registry to find out which VOEvent repository has the 
relevant record, then send a query to that repository asking for the 
record itself. The part of the identifier before the # symbol points to 
the repository itself; the identifier that includes the localID points 
to the event. Here is an example:

ivo://nvo.caltech/VOEventRepo
can be looked up in any VO registry, returning a description of the 
repository, such as who runs it, how many events it has, what is the 
service endpoint so it can be used.

ivo://nvo.caltech/VOEventRepo#60601
points to a specific VOEvent (number 60601) that is known to the 
Caltech VOEvent repository, but is not known to the VO registry. 


California Institute of Technology
626 395 3670
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