Using UCDs as tags
roy at cacr.caltech.edu
Wed Aug 13 09:07:13 PDT 2003
> I'd like to have your opinion on how to solve the sort of sql statement I
put at the
> end of my previous email:
> service_name, service_description, service_rowcount
> from Registry
> service_category = "CATALOG BROSWER"
> and data_class = "OBJECT CATALOG"
> and subject = "GALAXY"
> and querable_parameter = "GALAXY DISTANCE"
> and output_parameter = "GALAXY NAME"
> How would you make it work without a dictionary ?
Option (1) is the very successful and simple approach that Google takes --
matching words in the query with words in the descriptions of the resources.
Let us not forget this option!
Option (2) we can query on the UCDs. If I am looking for, say catalogs with
optical photometry, I would choose a suitable UCD, perhaps
"phot.flux.optical", and look for strong matches with UCDs in the output of
the services, or the queryable parameters, etc. The primary method of UCD is
a matching function: "how much are these UCDs alike?".
The data model people want a vocabulary that provides exact matches for all
astronomers. I believe this to be impossible. In contrast, the UCD approach
concentrates on finding "strong semantic matching".
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