2-stage identifier resolution

[Guy Rixon]

Roy,

that's a good summary of the resolution process. The formal name for the path
between the authority-ID and local-ID is "resource key" rather than
reasource-ID.

Paul Harrison points out that using # as a separator is naughty according to
W3C. In the W3C URI rules, # is always used to indicate a fragment of a
document available at a URI. Our local-ID part isn't exactly a fragment in the
W3C sense. The registry rules blessed ? as an alternate separator, so it might
be better to use that.

Mind you, nothing generically webbish will ever understand an ivo://... URI,
so there's no possibililty of confusion if we use # as a separator.

Cheers,
Guy

On Wed, 19 Apr 2006, Roy Williams wrote:

> 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

Guy Rixon 				        gtr at ast.cam.ac.uk
Institute of Astronomy   	                Tel: +44-1223-337542
Madingley Road, Cambridge, UK, CB3 0HA		Fax: +44-1223-337523