how to make a publisherDID

[Mark Taylor]

Pat,

URI permits a query part, so one possible way would be something like:

  ivo://cadc.nrc.ca/archive/cfht?observation=12345&product=raw

As far as I can see this would in principle solve the parsability 
issues you're looking at, and it's more flexible than putting 
everything in one hierarchical path.  It's probably a good enough
solution for human users.  However, given that it's not 
currently standardised, the answer to how a machine holding one 
of these actually works out what it means [still] relies on 
it's understanding your particular conventions for encoding 
the information in a URI.  Whether a human and/or machine actually
*needs* to understand what it means is another question, I'm not
involved enough with this stuff to have an opinion.

Mark

On Tue, 25 Oct 2011, Patrick Dowler wrote:

> I need to decide on a procedure for making publisherDID values for use in TAP 
> services, for example in the ivoa.ObsCore table, but also our internal CAOM 
> tables which also expose the same identifiers. This is following from the 
> interesting DAL-DM-DCP discussions on use of URIs.
> 
> Presumably, I could start with a DataCollection identifier registered in the 
> IVOA registry system, eg:
> 
> ivo://cadc.nrc.ca/archive/cfht
> 
> (note: more generally, a creatorDID would be linked to a DataCollection and a 
> publisherDID might be linked to a provider/service in case they are not the 
> same or definitive provider - let's ignore that for now)
> 
> In the past we would use the fragment, eg 
> ivo://cadc.nrc.ca/archive/cfht#12345/raw but that implies that one can somehow 
> "get" the entire collection and then look for "12345/raw" inside it (client 
> side). 
> 
> Instead, I could append some dataset-specific to get an observation identifier, 
> eg.
> 
> ivo://cadc.nrc.ca/archive/cfht/12345
> 
> and then append something product-specific to get an identifier for the product, 
> eg.
> 
> ivo://cadc.nrc.ca/archive/cfht/12345/raw
> 
> However, if someone has one of these (the last one), what can they do with it? 
> With this approach, there is no prescribed way to extract the identifier for 
> the registered DataCollection. Should there be?
> 
> In VOSpace, the spec invents a new URI scheme (vos) that prescribes exactly 
> how to extract/create the service URI from the vos URI, but it comes down to 
> being able to separate the URI into two halves: a base that can be looked up 
> in a registry and a separate bit (path in vos) that can be used when talking 
> to the service. In principle this does not require a new scheme, but it does 
> require at least a way to separate.
> 
> PS-I have the exact same issue with several services where I want to identify 
> the service with an ivo URI and I want to make and use URIs for items found 
> within/via that service.
> 
> -- 
> 
> Patrick Dowler
> Tel/Tél: (250) 363-0044
> Canadian Astronomy Data Centre
> National Research Council Canada
> 5071 West Saanich Road
> Victoria, BC V9E 2M7
> 
> Centre canadien de donnees astronomiques
> Conseil national de recherches Canada
> 5071, chemin West Saanich
> Victoria (C.-B.) V9E 2M7
> 

--
Mark Taylor   Astronomical Programmer   Physics, Bristol University, UK
m.b.taylor at bris.ac.uk +44-117-928-8776 http://www.star.bris.ac.uk/~mbt/