Extensions to VOResource - was Error column in VOResource

[Ray Plante]

I think Doug's comments reminds me what I think this issue comes down to, 
and that it is one of granularity of information in the registry.  I think 
in general we can't effectively answer this question without prototypes; 
furthermore, the right answer may change as the VO evolves.  

I suggested a metric that might be used to determine what goes into the
registry--i.e. whether it's used to select which resources are desired.  
Martin and Tony have presented cogent arguments as to why we might want to
go beyond that.  Doug mentioned another possible metric--what's static and
what isn't.

The approach to extensibility supported by the VOResource model is one 
that starts very general and coarse-grained (generic resources and 
services) and uses extensions to capture increasing levels of specificity.  
Some extensions will be standardized IVOA wide when it is clear that 
broad interoperability is needed at that level.  

So then much of the details of how we extend the resource metadata--in 
particular, what in metadata items we include--comes down to practical 
concerns (e.g. avoiding "metadata creep", what's easiest to standardize 
and get concensus on, etc.).  

cheers,
Ray