Identifying photometry filters

[Ray Plante]

Hi filter folks,

I have not been involved in the discussion of how to identify 
photometry filters and so I'm not up on the latest lines of reasoning.  
Perhaps what I'm going to share has been discussed; regardless, I 
thought it would be useful to put into the record an approach that 
leverages the Registry and the new StandardsRegExt couldl solve this 
problem.  

My starting assumption is that we want to provide a means to for 
creating unique way to identify a filter and to be able to use that 
identifier get the specific information that describes that filter.  

The StandardsRegExt provides a means for defining standard names for 
defined concepts.  Putting these definitions into a registry record 
creates IVOA-based URIs for each of the concepts.  In addition to 
the free-text description of each concept--in this case, a filter, 
the record includes a reference URL that should point to more 
information related to these concepts; both or either could provide 
details about the filter profile.  

The advantage of this means for identifying the URIs are as follows:
  o  there is an established way of dereferencing a URI to the 
       description of the filter.  
  o  it is easy to add new filter definitions
  o  while the IVOA may register "endorsed" filter descriptions, 
       anyone else may register their own.  

The biggest disadvantage, which I can imagine motivates Carlos' talk, 
is that the description of the filter is completely unstructured; some 
additional standard would be necessary if you wanted to provide 
specific terms for, say, the filter range.  

cheers,
Ray