resource identifiers

[Tony Linde]

Sounds good, Ray - you can be secretary at any meeting I'm in :)

Cheers,
Tony. 

> -----Original Message-----
> From: Ray Plante [mailto:rplante at poplar.ncsa.uiuc.edu] 
> Sent: 21 May 2003 15:23
> To: registry at ivoa.net
> Subject: resource identifiers
> 
> 
> Hi RWGers,
> 
> With the concensus reached on the general architecture for 
> registries at the Interop meeting and the general progress on 
> the RSM metadata, it's a good time to settle how we will 
> handle identifiers.  Several of us at the meeting reviewed 
> the discussion we had on the list back in February to try to 
> restate what we came up with in terms of our latest 
> architecture.  Below is a summary.  If I managed to get this 
> right, I can go ahead and write this up as a real IVOA proposal.  
> 
> First, some relevant items from the architecture:  
>   * everything is a resource (organization, data collection, 
> registry...)
>   * We have 3 types of registries: 
>       Full -- contains all resource descriptions known to the VO
>       Data Centre/Publisher -- contains only those 
> descriptions managed by
>   	a data center (for harvesting only)
>       Local -- contains a specialized subset of descriptions
>     All three types may have the ability to accept registration of new
>     resources. 
> 
> The primary purpose of a VO resource identifier is to serve 
> as a unique handle that can be given to a registry to get 
> back a description of that resource.  You can also use an 
> identifier to refer to some fine-grained item, such as an 
> image or catalog record--which is not explicitly registered 
> itself; for example, identifiers can be used to refer to 
> records in a catalog.  
> 
> Here's an example of what the ID for a registered resource 
> (say, an SIAP service) will look like in an XML context: 
> 
> <ResourceID>
>   <AuthorityID>ivo://www.ncsa.uiuc.edu/nvo/registry</AuthorityID>
>   <ResourceKey>ADIL/SIA/targeted</ResourceKey>
> </ResourceID>
> 
> As an SIA implementer, I might want to provide an identifier for each 
> image matching an image query (even though the image is not itself 
> registered anywhere); such an ID could look like this: 
> 
> <ResourceID>
>   <AuthorityID>ivo://www.ncsa.uiuc.edu/nvo/registry</AuthorityID>
>   <ResourceKey>ADIL</ResourceKey>
>   <RecordKey>95.DR.01.01.fits</RecordKey>
> </ResourceID>
> 
> Thus, an ID is composed of up to three components:
> 
>   * AuthorityID:  a globally unique URI that identifies a registry.  
> 
>       - all such IDs begin with "ivo://".  The "ivo" scheme signals
>         that the URI refers to a VO registry.
>       - It is recommended that the first field after the scheme be a
> 	DNS name in a domain controlled by the registry maintainer.
> 	This reduces the likelihood that two registries would have the
> 	same ID.  
>       - Often the URI will be easily converted to a URL (or base URL)
> 	that can be used for retrieving descriptions from the
> 	registry (e.g. substituting "http" for "ivo"); however, this
> 	is not a requirement.  
> 
>   * ResourceKey:  a string identifying the resource that is unique
>         within the publishing registry.  
> 
>       - This is ultimately the choice of the registry but may be a
>         combination of a name provided by the registrant and component
>         determined by the registry.
> 
>   * RecordKey:  a string identifying a component of a registered
> 	resource.  It is unique only with respect to the resource's
> 	ResourceKey and within the context that it is being cited.
> 
>       - This name is completely under the control owner of the
>         resource. 
>       - The key need not be permanent.  It may, for instance, refer to
>         an image cutout that does not permanently exist.
>         Alternatively, the item it refers to could be permanent (like
>         a record in a catalog) but the RecordKey is just a temporary
>         name used within a VOTable as part of a set of cone search
>         results.  
>       - There is no guarantee regarding how long a RecordKey is valid.
> 
> There will be many cases when one will want to refer to a 
> ResourceID as a single URI (such as in an OAI record).  In 
> general, this will be done using the following syntax:
> 
>    <AuthorityID>?resourceKey=<ResourceKey>&recordKey=<RecordKey>
> 
> That is, for the above two examples, 
> 
>    ivo://www.ncsa.uiuc.edu/nvo/registry?resourceKey=ADIL/SIA/targeted
>    
> ivo://www.ncsa.uiuc.edu/nvo/registry?resourceKey=ADIL&recordKe
> y=95.DR.01.01.fits
> 
> Did I get this right?
> 
> cheers,
> Ray
>