ISSUE-72 (lookup-table2): Bring back R2RML lookup tables [R2RML]

ISSUE-72 (lookup-table2): Bring back R2RML lookup tables [R2RML]

Raised by: Richard Cyganiak
On product: R2RML

This is part of the LC feedback on R2RML from Dominique Guardiola:

Before LC, work was done on a lookup table feature that allows translation from database values to arbitrary IRIs. Two different designs were proposed, one based on SKOS and one proprietary R2RML design. None of them made it into the LC spec, however.

Dominique says:

I think this decision is a pity : if you look from the point of view of future R2RML end-users , translation tables are a common pattern, which is present, for example in most web development frameworks or CMSs.

Anyone making SQL database knows it's better to use integers columns instead of verbose labels in order to :

- speed up queries
- allow the renaming of these columns labels easily
- avoid typos when these columns are also keys (when there's no foreign key constraint : think of MyISAM, probably one of the most common DB storage)

The use of SKOS here is a false question : it's true this looks like a "controlled vocabulary" situation, but I'd follow the argument stating that having properties like rr:value, rr:term is simpler for RDF newbies. I mean, a vocabulary choice question should not prevent you to provide this kind of simple feature.
Allowing the table to be linked elsewhere is important too, but could be added later, as could be more complex mapping techniques.

But removing this simple tool, a 1:1 code-to-string or code-to-URI table, from being part of the recommandation would send IMHO a bad signal to newcomers , like "hey, they didn't even think of a straightforward way to do that?"

Having to do pre-queries in a R2RML view just to fetch some labels in a separate table (that perhaps doesn't even exists, the labels list being hardcoded in the application code) is not really an answer.

Much of the discussion around the two designs is captured under ISSUE-61 and ISSUE-66.

Received on Monday, 7 November 2011 16:26:02 UTC