- From: Gustaf Neumann <neumann@wu-wien.ac.at>
- Date: Fri, 20 Apr 2001 23:00:29 +0200
- To: "Danny Ayers" <danny@panlanka.net>, "Brian McBride" <bwm@hplb.hpl.hp.com>
- Cc: "RDFInterest" <www-rdf-interest@w3.org>
On Friday 20 April 2001 18:47, Danny Ayers wrote: > Thanks for your reply, but I can't say that I'm particularly reassured. You > mention ways of possibly bending aboutEachPrefix and seeAlso into use. You > also give reasons why these aren't exactly ideal. You refer to a syntactic > include mechanism - have you got an existing one in mind, or woud this > need, erm... including? > > Let me suggest another scenario - I have 10000 documents on cheesemaking, > 5000 of these are by the same author, 5000 by another, half of the > documents are from one publisher half from another (not along author lines > or anything). You will surely agree that this metadata doesn't represent > much information. Ok, perhaps I could dynamically generate metadata, > perhaps I could hack XSLT to do what I wanted. Or of course I could repeat > the same information 10000 times inline with all the documents. > > The model for what's ideally needed is multiple inheritance, or at least > something approaching this. i believe that ***sharing*** of the information is the way to go. you will have a registry for a cheesmaker factory that produces something like <Cheesmaker rdf:ID="cm999"> <name>....</name> ... </Cheesmaker> and you refer from the cheesmaker to the appropriate cheesmaker ID. this is similar to good old normalization and might require something like a JINI like service. best regards -gustaf > From what your saying there is no 'natural' way > of doing this with RDF as it stands. If there might a relatively > straightforward way using what's already available, all well and good, > otherwise there's going to be some hassle not far down the line. Is this > deserving of a 'see also' at the bottom of the rdfms-abouteachprefix issue? > Maybe not. But I'm going to be looking at topic maps a bit more closely > from now on... > > Cheers, > Danny. > > > --- > Danny Ayers > http://www.isacat.net > > <- -----Original Message----- > <- From: Brian McBride [mailto:bwm@hplb.hpl.hp.com] > <- Sent: 20 April 2001 21:45 > <- To: Danny Ayers > <- Cc: Lee Jonas; Murray Altheim; RDFInterest > <- Subject: Re: Common Metadata (was:RE: RDF in XHTML) > <- > <- > <- Hi Danny, > <- > <- So the problem is, "How is common metadata to be represented in RDF > <- XML?" and you give a good example. > <- > <- Two ideas have been suggested: using aboutEachPrefix and using seeAlso. > <- > <- There is an issue listed regarding aboutEachPrefix: > <- > <- http://www.w3.org/2000/03/rdf-tracking/#rdfms-abouteachprefix > <- > <- One of the problems is that aboutEachPrefix is described in the syntax > <- but is not described in the model. This is pretty dodgy ground at the > <- moment because a lot of systems don't implement it. > <- > <- Even if one were to use aboutEachPrefix, where would the XML for those > <- statements be? In a separate document? How would a system find that > <- document, given one of your 1000 pages? > <- > <- Regarding seeAlso, the definition of seeAlso states: > <- > <- The property rdfs:seeAlso specifies a resource that might provide > <- additional information about the subject resource. > <- > <- So an RDF processor is not required to follow the link, but could do so. > <- However, what do you put in the see also document? > <- > <- <rdf:RDF> > <- <rdf:Description about="WHAT"> > <- <dc:creator>foo bar</dc:creator> > <- </rdf:Description> > <- </rdf:RDF> > <- > <- The problem is that the value of the about attribute is absolute, it > <- does not change its meaning depending on what link you followed to get > <- it. So > <- that doesn't seem to do what you need. > <- > <- A combination of seeAlso and aboutEachPrefix might do it. Put the > <- seeAlso in each document and use aboutEachPrefix in the 'see also' > <- document. But as I said, aboutEachPrefix is not widely implemented. > <- > <- A syntactic include mechanism might do what you are looking for. It > <- might then include say: > <- > <- <rdf:RDF> > <- <rdf:Description rdf:about=""> > <- <dc:creator>foo bar</dc:creator> > <- </rdf:Description> > <- </rdf:RDF> > <- > <- Note the rdf:about. There are problems here. First, a robot finding > <- the file to be included would see that it was created by foo bar, which > <- might well not be true. Secondly, XML isn't too good at being nested in > <- other XML at the syntactic level because of issues with things like > <- uniqueness of ID's and namespace prefix usage. > <- > <- However, for the range of things under your control, you could arrange > <- to > <- do this with say, an XSLT transform, to insert the meta data > <- automatically. This is not really an RDF solution. If I had an > <- immediate problem, I think this is the way I'd go. > <- > <- In terms of the issue list, I suggest you have highlighted an aspect > <- of the rdfms-abouteachprefix issue, and I'd propose to add a reference > <- to this thread under a 'see also' link under that issue. > <- > <- Brian > <- > <- > <- > <- Danny Ayers wrote: > <- > > <- > I can't see how RDF could be practical without some mechanism for > <- > inherited/shared metadata (you've got a 1000 documents with the same > <- > author - do you need to specify this a 1000 times), but I'm > <- thinking that > <- > because this is so significant it must have been dealt with already - > <- > seeAlso doesn't really seem adequate, I'm not sure of the history of > <- > aboutEachPrefix, but surely there is already some mechanism in > <- place? Lee's > <- > xsl:include/import suggestion sounds possible. If this angle is well > <- > covered, an idiot's guide is needed (for this idiot at least), > <- otherwise I > <- > think it could well be an issue. > <- > > <- > --- > <- > Danny Ayers > <- > http://www.isacat.net > <- > > <- > <- -----Original Message----- > <- > <- From: www-rdf-interest-request@w3.org > <- > <- [mailto:www-rdf-interest-request@w3.org]On Behalf Of Lee Jonas > <- > <- Sent: 20 April 2001 19:47 > <- > <- To: 'Danny Ayers'; Murray Altheim > <- > <- Cc: RDFInterest > <- > <- Subject: RE: RDF in XHTML > <- > <- > <- > <- > <- > <- > <- > <- > <- > <- Danny Ayers [mailto:danny@panlanka.net] wrote: > <- > <- > <- > <- ><- The RDF Schema spec hints at 'rdfs:seeAlso' for > <- cascading purposes, > <- > <- e.g.: > <- > <- ><- > <- > <- ><- <rdf:RDF ...(namespaces)...> > <- > <- ><- <rdf:Description rdf:about="" rdfs:seeAlso="furtherinfo.rdf"/> > <- > <- ><- </rdf:RDF> > <- > <- > > <- > <- >Looks viable - I wonder if there's anything more than hints > <- > <- >this is rather important, probably well known (but I can't > <- > <- think of it) - > <- > <- >what is the best way to use inheritance of metadata > <- between documents? > <- > <- >How do I avoid adding the same author information to every > <- one of the > <- > <- >million pages I've written (with the aid of some monkeys)? > <- > <- > > <- > <- > <- > <- Well, this is an entirely different prospect, and one I > <- think that the > <- > <- 'rdf:aboutEachPrefix' predicate was intended to address. > <- > <- However, AFAIK it > <- > <- has a lot of opposition due to the fact that it is difficult to > <- > <- implement in > <- > <- practise, e.g.: > <- > <- > <- > <- 1) Consider starting with a resource and trying to determine who > <- > <- the author > <- > <- was. If this info is in a 'rdf:aboutEachPrefix' statement in > <- > <- some other rdf > <- > <- doc, not even referenced from the resource you are currently > <- > <- processing, it > <- > <- is nigh on impossible to determine. > <- > <- > <- > <- 2) It relies upon the hierarchical location of resource > <- representations - > <- > <- the granularity of what these kinds of statements apply to is > <- > <- too course - > <- > <- i.e. all resources whose URIs 'startWith' a common substring. It > <- > <- might have > <- > <- been better to do something akin to what XPointer does for XML. > <- > <- > <- > <- Suggestion: > <- > <- IMHO rdf:seeAlso is equivalent to xsl:include semantics. What > <- > <- is lacking is > <- > <- xsl:import semantics. The latter might allow you to define a set > of <- > <- statements that apply to their current doc, then 'importing' <- > > <- that doc from > <- > <- another would make those same statements apply to the doc doing the > <- > <- importing. Hence, importing a handful of rdf docs containing > common <- > <- statements (e.g. author) from a million XHTML web pages > would <- > <- save a lot of > <- > <- typing! > <- > <- > <- > <- This would solve both 1) and 2) above to some degree of > <- > <- satisfaction - the > <- > <- degree of satisfaction of 2) depends on how you structure > <- your imported > <- > <- docs. Is this worthy of the issues list? > <- > <- > <- > <- > > <- > <- > > <- > <- ><- >On another line, forget XHTML for a moment, how do we embed > <- > <- metadata in > <- > <- ><- >other XML markups? > <- > <- ><- > <- > <- ><- I thought this is what XML Namespaces are for! Just embed your > <- > <- elements, > <- > <- ><- any processor that doesn't recognise the namespace (within its > <- > <- ><- context) can > <- > <- ><- ignore it. Note that to validate such documents > <- properly (and allow > <- > <- such > <- > <- ><- open mixing-and-matching of different 'XML mini-languages') > will <- > <- ><- require XML > <- > <- ><- Schema. > <- > <- > > <- > <- >Quite. (to avoid this going in circles, please ignore) so why > <- > <- should XHTML > <- > <- >be treated any different? > <- > <- > <- > <- One reason is that it is currently validated using a DTD. > <- Whether XML > <- > <- Schema would fare better, I don't altogether know for sure. > <- > <- > <- > <- (Note that my current understanding of XML Schema is not > <- perfect, I am > <- > <- hoping that XML Schema allows you to freely mix-and-match > <- elements in > <- > <- different XML namespaces.) > <- > <- > <- > <- regards > <- > <- > <- > <- Lee > <- > <- > <-
Received on Friday, 20 April 2001 17:01:21 UTC