- From: Pat Hayes <phayes@ihmc.us>
- Date: Tue, 21 Dec 2004 19:24:51 -0800
- To: "Seaborne, Andy" <andy.seaborne@hp.com>
- Cc: Steve Harris <S.W.Harris@ecs.soton.ac.uk>, RDF Data Access Working Group <public-rdf-dawg@w3.org>
>Steve Harris wrote: >>On Sun, Dec 19, 2004 at 09:01:05 -0600, Dan Connolly wrote: >> >>>>My engine has no way to turn off inference (though it wouldn't be hard to >>>>add globaly), but I'd like it if that was possible on a per-statement way >>>>via the query language. >>> >>>I'm not sure what you mean; it makes more sense, to me, to specify what >>>you're querying against in the FROM clause. If we wanted explicit >>>support for "turning RDFS inferencing off" in SPARQL, I'd expect it >>>to look something like: >>> >>> SELECT ?C FROM rdfs(<mydata.rdf>) WHERE ( :x rdf:type ?C). >>>vs. >>> SELECT ?C FROM <mydata.rdf> WHERE ( :x rdf:type ?C). >> >> >>[turning off wasn't really what I was thinking of, but I cant think of a >>better term, ignoring maybe] >> >>OK, well I would expect it to look more like >> >> SELECT ?C WHERE GROUND (:x rdf:type ?C) >> >>I dont really like FROM as it doesn't make much sense in server-like >>systems where all the graphs are preloaded (for performance or security >>reasons), or systems that are reflecting underlying data in another format >>and translating queries on the fly. > >FROM could make sense - the server offers a numer of graphs and the >URI in teh FROM must choose one of them. If it names some graph the >server is not publishing, then the query generates an error. FROM >isn't a requirements to load any graph (I worry about the security >issues of that). A server may require that there is only one URI in >the FROM clause - i.e. no arbitrary RDF merge of graphs. It is just >a request for something that the server does not offer. Agreed. I think we should allow a server to refuse to answer a query if it names FROM a graph that the server cannot (prefers not to) access, and we should allow the query to provide a variable in the FROM position which gets bound to the name of the source as part of the answer, so that a query can say, in effect: answer this from any source you choose, but tell me what the source was. Query-answering servers should be required to provide a binding to any such variable, even if it is a 'trivial' one which simply identifies the server itself (which means, roughly: I am the source, and that's all you are going to get out of me on that topic.) BTW, there should not be a requirement on a server that the same query from the same source will produce the same result each time. But it might be useful to enable a server which does undertake to be stable in this way, to advertise the fact that it is stable. Pat >(This use of FROM is one mode for Joseki I'm considering) > > Andy > >> >>- Steve -- --------------------------------------------------------------------- IHMC (850)434 8903 or (650)494 3973 home 40 South Alcaniz St. (850)202 4416 office Pensacola (850)202 4440 fax FL 32502 (850)291 0667 cell phayes@ihmc.us http://www.ihmc.us/users/phayes
Received on Wednesday, 22 December 2004 03:25:46 UTC