- From: Kingsley Idehen <kidehen@openlinksw.com>
- Date: Tue, 09 Mar 2010 07:00:49 -0500
- To: Hugh Glaser <hg@ecs.soton.ac.uk>
- CC: Bernhard Schandl <bernhard.schandl@univie.ac.at>, Peter Ansell <ansell.peter@gmail.com>, Aldo Bucchi <aldo.bucchi@gmail.com>, Linked Data community <public-lod@w3.org>
Hugh Glaser wrote: > I have found this a very interesting discussion, thinking about the Linked > Data World at large as well as what others think - thanks. > Sorry this moved away from the important discussion about how to identify > people, both as a technical and a socio issue - my fault. > Hugh, Nice discussion, I don't think anyone found it divergent or distracting :-) As per usual, you triggered broader discussion of some issues that have been rumbling under the surface for a while. I am sure Aldo is much clear about options for easy generation of Identifiers etc.. Kingsley > On 09/03/2010 09:12, "Bernhard Schandl" <bernhard.schandl@univie.ac.at> > wrote: > > >> Peter, >> >> >>> It is a good thing that the subject URI is an HTTP URI available from >>> your server but that is only the start of the story. The rest of the >>> story needs other servers to give your data more context. >>> >>> >>>>> In your example the fact that there >>>>> is a link can only be figured out using some external service that >>>>> knows about both data sources. >>>>> >>>> Sure. Before I can add a link to any data set, I have to detect it using >>>> some heuristics. Shared URN/DOI/... identifiers seem a valid approach for >>>> this -- think of ISBN numbers. >>>> >>> Sharing identifiers is a good idea, but it isn't Linked Data as yet... >>> >> I'm talking of the *preconditions* for linking data, based on shared >> identifiers. And once I have these identifiers, why not publish them alongside >> the dereferenceable URIs. >> > Being able to work out what a dereferenceable URI means is indeed a > pre-condition for linking data, and also in the Linked Data, this is > achieved by dereferencing and examining the RDF returned. > And finding a URN, doi, isbn, mailto, etc. is a very good way of > communicating that information. > However, for me in the Linked Data world, such URIs are no more an > *identifier* than "Hugh Glaser", or the title of a book, (or even the URL of > one of my homepages) simply because the access mechanism is unclear, and > even if I do try to look it up I am unlikely to get RDF (at least at > present). > They are more useful in general, of course, because they are less likely to > be ambiguous, but it is only a matter of degree. > >>>>> If your server was Linked Data and not >>>>> just an HTTP URI based RDF database then it would link out using HTTP >>>>> URI's and both servers could be directly explored without some >>>>> external service. >>>>> >>>> Once the link has been detected, I can of course add it to both data sets. >>>> Well, the owner of the datasets can. >>>> >>> This is Linked Data, when the dataset owners discover the mutual >>> references and link out from their HTTP URI's to the other datasets >>> HTTP URI's. >>> >> Why only the dataset owners? A third party that is aware of both data sets is >> enabled to discover these links, too. >> > I agree entirely, although the dataset owner is in a prime position to seed > the activity, and also may have other implicit knowledge that is useful to > help to get the links right. > >>> It was enabled by sharing the property, and then having >>> others discover it. Just sharing the URN property isn't Linked Data as >>> people have no way of resolving the URN that is referenced to more >>> information. >>> >> Again, it's a precondition to link data. >> >> >>> It could also have been shared in another way using Inverse Functional >>> Properties (IFP) so that the URN scheme need not have been created. >>> >> The URN schema for ISBN already exists [1], and several others exist (e.g., >> SWIFT [2]), why should we throw them away? >> >> [1] <http://www.faqs.org/rfcs/rfc3187.html> >> [2] <http://www.faqs.org/rfcs/rfc3615.html> >> >> >>> There is no automatic HTTP based way of knowing which datasets may >>> have relevant links in either case, >>> >> One could use indices to find other occurrences of the same URN. When they are >> linked via owl:sameAs, the linking can be fully automatized. >> >> >>> so serving up the statements on >>> your dataset is very useful for discovery, I wasn't meaning to say >>> that was a bad thing. Just emphasising the full story for Linked Data. >>> >> I got that :-) >> >> My point is simply that not *every* URI in a Linked Data context needs to be >> dereferenceable. When there are established URN schemes in place (like it is >> the case for ISBN numbers), why not reuse them instead of packing them in a >> literal (is there a datatype for ISBN numbers?) and publish them to simplify >> linking for others? This seems to make more sense to me than only relying on >> URN-to-HTTPURI mappings, which I can still do, as long as I publish the >> "original" identifier in its "native" URN form. >> > I have a feeling that the issue here may be the same as how to represent the > address of someone's pure html home page in RDF. > It is a URL and hence a URI. But it is not dereferenceable to RDF. > A purist might say that it is not a Linked Data URI (doesn't return RDF), > and so should be a string, hopefully with a useful type on it. > But for others it is a resource, and so can comfortably be a URI in RDF. > And having it as a resource enables it to be used in a more convenient way > for the sort of thing that we are discussing. > So dereferencing one of your Linked Data URIs will return some RDF that has > resources (URIs) that are not dereferenceable to RDF. > And these will be very helpful to people/agents who are trying to add > linking to the world. > > Hopefully that is sufficiently closely related to your comments to make > sense? > And I am pleased to agree, although I might lean more to the purist side :-) > > By the way, in the original question, there seemed to be a suggestion which > I guess I misunderstood, that an RDF store that effectively only published > non-dereferenceable URIs, and accessed as a query service, was in some sense > doing Linked Data. I would have found that very hard to agree with. > > Best > Hugh > >> Best >> Bernhard >> >> > > > -- Regards, Kingsley Idehen President & CEO OpenLink Software Web: http://www.openlinksw.com Weblog: http://www.openlinksw.com/blog/~kidehen Twitter/Identi.ca: kidehen
Received on Tuesday, 9 March 2010 12:01:20 UTC