- From: Pat Hayes <phayes@ai.uwf.edu>
- Date: Wed, 27 Feb 2002 11:22:06 -0600
- To: Frank Manola <fmanola@mitre.org>
- Cc: w3c-rdfcore-wg@w3.org
>At the risk of further complicating this discussion, let me give my >interpretation, for what it's worth, of the M&S material in question, >i.e., > >[[ (P221) The xml:lang attribute may be used as defined by [XML] to >associate a language with the property value. There is no specific data >model representation for xml:lang (i.e., it adds no triples to the data >model); the language of a literal is considered by RDF to be a part of >the >literal. An application may ignore language tagging of a string. All RDF >applications must specify whether or not language tagging in literals is >significant; that is, whether or not language is considered when >performing >string matching or other processing.]] > >I'd first observe that the XML spec cites as an example of using >xml:lang distinguishing between > ><p xml:lang="en-GB">What colour is it?</p> and ><p xml:lang="en-US">What color is it?</p> > >Then a few observations based on P221: > >1. "There is no specific data model representation for xml:lang (i.e., >it adds no triples to the data >model)". That is, the lang attribute isn't explicitly reflected in the >"data model" *as triples* > >2. The problem is interpreting what "the language of a literal is >considered by RDF to be a part of the >literal" means. Brian says it means that a literal is really >(effectively) a pair. Patrick says the language is non-existent in the >RDF graph. > >3. P221 also says: "All RDF applications must specify whether or not >language tagging in literals is >significant; that is, whether or not language is considered when >performing string matching or other processing." [Note: RDF >application, not XML application]. If the language tagging is not >available in what an RDF application processes, this doesn't appear to >make any sense; the application would have nothing to consider. If an >RDF application always processes an XML serialization, things would be >OK. But if an RDF application only processes triples (not an XML >serialization), it seems to me we need to do one of two things: > >a. dispense with most, if not all, of P221: not just the part that >says that the language is considered part of the literal, but also the >part that talks about RDF applications possibly considering language >tagging in string matching and other processing. > >b. accept that the language information is *somehow* there in the >literal (although the M&S doesn't say how). Effectively, that sounds >like a pair. > >[actually, maybe there's a c.: change what we mean by "RDF >application") Let me suggest a possible way out of this maze. Its the kind of thing that a mathematician would say, so maybe it won't be acceptable, but here goes. Literals are strings. However, an app might decide that what counts as the 'same' string for inference purposes might be language-sensitive, so that the UK-spelling string "What colour is it?" might be allowed to match, ie to be the 'same as' the US-spelling string "What color is it?". Such language-sensitive matching would require an application which used it to maintain language tags associated with literals, but those tage are invisible to RDF, and are not considered to be part of the RDF graph syntax. If an RDF application uses language-sensitive matching then it will be able to draw more conclusions than one which does not, for example ex:Nigel ex:believes "color is red" . ex:BillyBob ex:believes "color is red" . might have the consequence ex:Nigel ex:believes _:x . ex:BillyBob ex:believes _:x. with language-sensitive stringmatching, but would not if simple string matching were used. IN mathematical terms, a literal is in general an equivalence class of strings, but the criteria that determine equivalence are under the RDF hood. And if there isnt anything under the hood, then every class just has a single string in it. This would I think allow Brian to preserve his code with a clear conscience, but also would avoid the issues that arise from saying that languages were anything like properties. (?) Pat PS. One case which this might not handle well would be where the one string means different things in different languages. Are there any cases like that? -- --------------------------------------------------------------------- IHMC (850)434 8903 home 40 South Alcaniz St. (850)202 4416 office Pensacola, FL 32501 (850)202 4440 fax phayes@ai.uwf.edu http://www.coginst.uwf.edu/~phayes
Received on Wednesday, 27 February 2002 12:22:13 UTC