- From: Kjetil Kjernsmo <Kjetil.Kjernsmo@computas.com>
- Date: Mon, 16 Mar 2009 10:37:09 +0100
- To: "public-rdf-dawg@w3.org" <public-rdf-dawg@w3.org>
All, We've been happy users of DESCRIBE queries in two commercial projects now, I we want to continue using them. We do feel, however, that it needs a bit of elaboration. What we are requesting is mostly a clearer spec, nit necessarily a new feature. We are somewhat confused about the effect named graphs have on DESCRIBEs, but I will address that in a separate email. We feel that it was a good thing that the DAWG did not specify the result graph in SPARQL 1.0. We also feel that DESCRIBE still should not specify a single result graph. For an example of why we came to this conclusion, we think that an endpoint for a weather service would reasonably return something different for DESCRIBE <http://sws.geonames.org/3146631/> than a pure Geonames endpoint. The former may return something like <http://sws.geonames.org/3146631/> a gn:Feature ; gn:name "Lysaker" ; w:latest_forecast <http://example.org/forecast/2009/03/14> . <http://example.org/forecast/2009/03/14> w:Forecast ; w:text "Cloudy" . Whereas the pure Geonames endpoint may only want to return properties of the gn:Feature. Nevertheless, we think that we should specify a "default implementation". We have found that this is important to be able to migrate with little cost between database systems, which is an important aspect of a standard. We think that we should develop a default result set that every SPARQL implementation should support, but allow it to be overridden by server administrator. Furthermore, when specifying it, we should keep in mind that the DESCRIBE is most useful as a "give me all you know about http://example.org/foo"-type query. The DESCRIBE should therefore return enough information to allow an agent to present this information to a human. The Concise Bounded Description http://www.w3.org/Submission/CBD/, which was some of the input to DAWG in the previous round, is a useful starting point (except, perhaps the reification stuff). It doesn't really help in presenting the data to human, however. It may be an idea to include rdfs:labels, if they exist for classes and properties, for example, as this is useful when presenting to a human user. Anyway, the specification of the result graph is something that we do not have very strong opinions about. What we do feel strongly about is that there is a such a result graph that all endpoints should implement, and that DESCRIBE is formally specified. Kind regards Kjetil Kjernsmo -- Senior Knowledge Engineer Mobile: +47 986 48 234 Email: kjetil.kjernsmo@computas.com Web: http://www.computas.com/ | SHARE YOUR KNOWLEDGE | Computas AS PO Box 482, N-1327 Lysaker | Phone:+47 6783 1000 | Fax:+47 6783 1001
Received on Monday, 16 March 2009 09:37:37 UTC