definition of registry

Patrick Dowler patrick.dowler at
Wed Apr 30 10:52:52 PDT 2003

On April 30, 2003 10:34, Robert Hanisch wrote:
>     A registry is used to identify and locate resources satisfying
> user-specified criteria, and to direct more detailed information
> requests to
> the relevant services.

On April 30, 2003 10:02, Ray Plante wrote:
> A few items to think about with regard to approaching queries to
> registries.
> 1.  Overlap with VOQL WG:

These two points together indicate something that - frankly - scares me about
the current thinking in the registry WG: there is way too much detail at the
registry level that really belongs in the service(s) themselves. 

As Bob said, "direct more detailed information requests to the relevant 
services". The goal is the registry is to find those relevant services too 
which is is worth sending the real query. That doesn't men that every one of 
those services will actually have results to provide. It means they might
have results. 

If you think about services in a very simplistic key=value sense (just for
elucidation of my point - clearly insufficient) then the service is able to 
answer questions like "how many key1=X do you have?" while the registry
should do no more than "how many services know about key1?" The registry 
should have no concept of what the values are in any one service.

>From a practical point of view, it is very simple for a client to send the 
same query (i.e. VOQL) to many services that know about "key1" and 
happily deal with the fact that most return 0 things. It is trivial in general 
for a service to process queries that return 0 things.

So, lets avoid overlap between registry and QL. We don't need to implement the 
whole VO in the registry, after all :-)

Patrick Dowler
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