1. Should we specify all possible values ? There is the suggestion in the current document to allow the value 'other' when no available category fits to describe a possible science data product.
2. If we allow other , how do we specify more information ? In free format, in Subtype, but then no interoperability is granted.
3. How could we suggest a possible set of pairs (type, subtype) for a data product and provide examples

Comments

In my opinion, in an ideal world this would be something like a set of tags (e.g., it's easy to imagine spectrum-image, or spectrum-timeseries, or image-timeseries). A taxonomy of such classes (the "tree") could then be used for query expansion by clients. However, there are no set-valued columns in ADQL, and faking them using, e.g., strings and SQL patterns ("=AND producttype like '%/spectrum/%'=") would defeat indexing and simply be ugly. So, I'd say make a catalog, ideally using the StandardKeyEnumeration from StandardsRegExt, and "other" is simply the SQL NULL. Tell both data providers and consumers not to fill in the type if there's not a good match. Ideally, the StandardKeyEnumeration would in the descriptions try to cover as many real data products as possible ("This category covers objective prism exposures"). My feeling is that that's the Pareto-correct way of doing things, actually covering probably around 98% of the actual queries rather than just 80%. -- MarkusDemleitner - 04 Mar 2011