Resource Identifiers and Resource Type Identifiers

[Paul Harrison]

As the VO grows bigger it likely that we will be deploying several 
instances of the same type of service. There are two cases that I can 
think of

a) failover - where the service instances would be idential clones
b) same functionality, different algorithms - e.g. there could be 
several services providing photometric redshifts

In both these cases if writing code to hunt the registry there needs to 
be a way of hunting for specific instances of service as well as being 
able to search for types or classes of service.

In the schema it seems that the vr:Identifier for a vr:ServiceType 
fulfils the role of uniquely specifiying a service instance, however in 
the case of specifying the type of a service the situation appears to be 
more ambiguous.

There are;

vr:LogicalIdentifier
vr:RelatedResource
vr:Capability

each of which could conceivably be used to specify the "type" of the 
service. I am interested to gather opinions about this from the 
community, as I think it would be good to have a convention (that could 
perhaps be enshrined by making the schema more strict on one of the 
above elements) for identifying service types. Since, as mentioned above 
(and has already recognised in the case of UCDs), it is essential to 
have well defined names for types to be able to write software more easily.



-- 
Dr. Paul Harrison, Astrogrid Programmer
MERLIN/VLBI National Facility, University of Manchester,
Jodrell Bank Observatory, Macclesfield, Cheshire SK11 9DL, U.K.
tel +44 (0)1477 572681 (direct), 571321 (switch) - 07904025192 (mobile).