- From: Yves Raimond <yves.raimond@gmail.com>
- Date: Fri, 2 Jan 2009 23:20:52 +0000
- To: "Richard Cyganiak" <richard@cyganiak.de>
- Cc: "Aldo Bucchi" <aldo.bucchi@gmail.com>, "public-lod@w3.org" <public-lod@w3.org>
Hello, and happy new year! > Happy new year to all LODers! 2009 will certainly be another interesting > year around here! > > > Aldo, > > The issue you describe below has been discussed in a long thread back in > 2007. We mostly talked about a slightly different problem -- where a > resource description would include a very large number of values for a > particular property -- and therefore we want to move those triples into a > separate document that is somehow reachable from the resource description. > But a solution to that problem would likely also solve your problem (you > have just a single value for the property but it's expensive to compute and > should therefore be retrieved in a separate HTTP call). > > I proposed this solution: > http://simile.mit.edu/mail/ReadMsg?listName=Linking%20Open%20Data&msgId=20926 > > And some refinements here: > http://simile.mit.edu/mail/ReadMsg?listName=Linking%20Open%20Data&msgId=20962 > > This is actually based on some side comments that TimBL made in his original > Linked Data document -- I think he saw this problem coming. > > I started a page on the ESW wiki back then: > http://esw.w3.org/topic/SeparateDocumentsForLongPropertyLists > > There was no real conclusion to the thread, and no formal proposal was > written up, just a problem statement. That's because we couldn't really > reach consensus. Others were pushing for a more flexible and complex > solution than the one I describe in the links above. See here -- it's the > "arcs" proposal: > http://simile.mit.edu/mail/ReadMsg?listName=Linking%20Open%20Data&msgId=20930 > http://simile.mit.edu/mail/ReadMsg?listName=Linking%20Open%20Data&msgId=21015 > > I wonder what people think about this issue now, and if we can get closer to > a workable proposal. I'm willing to spend some cycles on the writeup and > preparing the vocabulary if we can reach some rough consensus. > This discussion was indeed interesting :) I now tend to think that linking to a separate document is a cleaner way to go, but I am still concerned about auto-discovery. When you see something like: :New_York :morePersonsBornHere <http://example.org/persons_nyc.rdf> . in the representation of :New_York, you still need a way to describe the fact that :morePersonsBornHere links to a document holding lots of :birthPlace properties. Just saying that :morePersonsBornHere rdfs:subPropertyOf rdfs:seeAlso won't do the job properly - how can you tell before retrieving the whole document? But perhaps the approach I proposed when we discussed the void:example property could work, in exactly the same way as in [1]. In the representation of :New_York, we could write something like (in N3): <http://example.org/persons_nyc.rdf> void:example { :al_pacino :birthPlace :New_York }. Then, a SPARQL query like the following could find the documents that hold information about persons born in New York: SELECT ?doc WHERE { ?doc void:example ?g . GRAPH ?g { ?person :birthPlace :New_York . } } One of the good thing with this approach is that the "patterns" of information held in the target document can be arbitrarily complex - and the only thing you have to do is to provide an example RDF graph, holding something representative of what you put in that document. Cheers! y [1] http://blog.dbtune.org/post/2008/06/12/Describing-the-content-of-RDF-datasets
Received on Friday, 2 January 2009 23:21:28 UTC