datasets and registries

[Doug Tody]

On Thu, 18 Sep 2003, Tony Linde wrote:

> <<I hope that the registry will be able to tell me which services exist 
> that can recognise an ID that matches the  ivo://NASA/HST part >>

The above appears to be asking about service discovery for data access
services that can return data from a data resource (collection) called
ivo://NASA/HST.  In this case there can be many registered services which
can return data from the above referenced resource, a data collection.
Also the data collection may be replicated at multiple locations.
 
> The registry will tell you the ONE resource that matches ivo://NASA/HST,
> since this is a unique resource identifier (where NASA is the AuthorityID
> and HST is the ResourceKey). The metadata returned for that resource will
> tell you the URL of that web service. The standard methods of such a service
> are yet to be agreed, but I would assume one is a doQuery(string AdqlQuery)
> type of method.

This however appears to refer to how one queries the registry for the
metadata for a specific registered resource such as a data collection.
I am not sure what the web service is that is being referred to.  What does
this web service do - is it part of the registry mechanism?  If it is a
data access or other such service I would not expect it to be referenced
in the registered metadata for the data collection.  There may be any
number of such services that reference a particular resource such as a
data collection, hence they must be registered and described independently.
Dynamic discovery, via registry queries, is where the association is made.

	- Doug