- From: Phil Archer <phila@w3.org>
- Date: Wed, 24 Aug 2016 09:26:19 +0100
- To: Jeremy Tandy <jeremy.tandy@gmail.com>, Linda van den Brink <l.vandenbrink@geonovum.nl>, Bill Roberts <bill@swirrl.com>
- Cc: SDW WG Public List <public-sdw-wg@w3.org>
Bill's comments also made me think about some of the classic arguments, such as that a lake doesn't have a last updated date and isn't 435KB big. Which are true, however, that kind of metadata generally comes from the server, i.e. the HTTP layer. That's an over simplification but the point is that it is relatively easy to avoid deliberately creating misleading metadata - metadata about the doc rather than the thing it describes - and it's also generally easy to avoid looking for that metadata. Is there scope for some BP advice there? Phil. On 24/08/2016 08:25, Jeremy Tandy wrote: > Thanks Linda. More clear examples where being "correct" (in terms of > avoiding uri collisions by using two distinct uris) is making things worse > because users take the wrong one! > > So, as a WG, are we content to recommend this "indirect identification" > pattern where thing & info resource identifiers are conflated? > > Bill has added some good points about how to avoid impacts of uri > collision- by using the (dataset) metadata to talk about licenses and > creators for the information ... > On Wed, 24 Aug 2016 at 07:52, Linda van den Brink <l.vandenbrink@geonovum.nl> > wrote: > >> Experience from the Netherlands: we have the id/doc pattern in our URI >> strategy, based on the Cool URIs note [8] and the ISA study on persistent >> identifiers [9]. >> >> >> >> That being said, same as Bill I also notice data users getting confused >> and generally using the /doc/ URI as that is the one they can copy from >> their browser address bar. This is not only casual confusion but also ends >> up in published information resources. >> >> >> >> You see this, for example, all over the CB-NL which is a vocabulary for >> the building sector and contains links to other Dutch standards such as >> IMGeo, an information model and vocabulary for large scale topography. E.g. >> the CB-NL concept of ‘Gebouw’ (Building) [10] links to two IMGeo concepts >> ‘Pand’ (building part) and ‘Overig Bouwwerk’ (other construction) using >> their /doc/ URIs. If you click on Pand (which doesn’t have its own landing >> page in CB-NL so I can’t include the link) you will see it includes the >> /doc/ URI as the identifier of Pand. >> >> >> >> This is an example where it occurs in vocabularies, but I also see it >> happen with identifiers for data instances. >> >> >> >> [8]: https://www.w3.org/TR/cooluris/ >> >> [9]: >> https://joinup.ec.europa.eu/sites/default/files/D7.1.3%20-%20Study%20on%20persistent%20URIs_0.pdf >> 10: http://ont.cbnl.org/cb/def/Gebouw >> >> >> >> Linda >> >> >> >> *Van:* Jeremy Tandy [mailto:jeremy.tandy@gmail.com] >> *Verzonden:* dinsdag 23 augustus 2016 20:57 >> *Aan:* Bill Roberts >> *CC:* SDW WG Public List >> *Onderwerp:* Re: Clarification required: BP6 "use HTTP URIs for spatial >> things" >> >> >> >> Thanks Bill. Sounds very coherent ... I hoped for some responses such as >> this based on practical experience. Jeremy >> >> On Tue, 23 Aug 2016 at 19:41, Bill Roberts <bill@swirrl.com> wrote: >> >> ah Jeremy, you are a brave man to poke the sleeping beast of httpRange-14. >> >> >> >> But I'll get my thoughts in early, then I can tune out of the ensuing mail >> avalanche :-) >> >> >> >> When publishing Linked Data about places we (at Swirrl) generally do the >> id/doc fandango, but to be honest I think data users either don't notice, >> or they get confused by it. In the applications we are working with (and I >> acknowledge that others may have different applications and different >> experiences), it wouldn't cause any problems to have a single URI, the 'id' >> URI if you like. We just don't find a need to say anything about the /doc/ >> URI. If we were starting again, I'd probably ditch the /doc/ and the 303 >> and rely on context and a little bit of documentation to make it clear what >> we mean. >> >> >> >> The place where we find a need to talk about creators and licences and >> modified dates is in metadata about datasets where a dataset might be a >> collection of information about a bunch of places - and we treat datasets >> as an 'information resource'. If someone requests a dataset URI we return a >> status code of 200 and the dataset metadata as the response. That metadata >> includes info on where to get all the contents of the dataset if you want >> that. >> >> >> >> By the way, though it's sensible and consistent, I find that the implied >> and parallel property stuff makes it more rather than less complicated. >> >> >> >> Bill >> >> >> >> >> >> >> >> >> >> >> >> >> >> On 23 August 2016 at 17:37, Jeremy Tandy <jeremy.tandy@gmail.com> wrote: >> >> All- >> >> >> >> Linda has done a great job of consolidating the best practices are use of >> identifiers. We have just one [1] now. >> >> >> >> Reading though just now, it occurred to me that there's still an open >> issue about identifier assignment ... >> >> >> >> W3C's Architecture of the World Wide Web constraint "URIs identify a >> single resource" [2] asserts "Assign distinct URIs to distinct resources" >> in order to avoid URI collisions [2a] which "often imposes a cost in >> communication due to the effort required to resolve ambiguities". >> Discussions from earlier years in UK Gov Linked Data working group (and >> elsewhere) concluded that the "real world thing" and "information resource >> that describes the real world thing" are separate resources. I think this >> is based on a (purist?) view when working with RDF of needing to be totally >> clear on "what's the subject" of each triple ... the thing or the document. >> This manifests as URIs with `id` or `doc` included somewhere to distinguish >> between the resources and some RDF triples to clarify that the doc resource >> is talking about the thing resource etc.. >> >> >> >> (dangerously close to "httpRange-14" [3] here ... let's avoid that bear >> trap) >> >> >> >> Jeni Tennison's "URLs in Data Primer" draft TAG note captures this >> practice in §5.3 "Publishing data" [4]: >> >> >> >> ``` >> >> Publishers can help enable more accurate merging of data from different >> sites if they support URLs for each entity >> <https://www.w3.org/TR/urls-in-data/#dfn-entity> they or other sites may >> wish to describe, separate from the landing pages >> <https://www.w3.org/TR/urls-in-data/#dfn-landing-page> or records >> <https://www.w3.org/TR/urls-in-data/#dfn-record> that they publish. >> >> ``` >> >> >> >> Yet Architecture of the World Wide Web §2.2.3 "Indirect identification" >> [5] notes that: >> >> >> >> ``` >> >> To say that the URI "mailto:nadia@example.com" identifies both an >> Internet mailbox and Nadia, the person, introduces a URI collision. >> However, we can use the URI to indirectly identify Nadia. Identifiers are >> commonly used in this way. >> >> ``` >> >> >> >> This is consistent with what I recall TimBL saying at TPAC-2015 in regards >> to Vcard; come the finish, no one really cares to distinguish between the >> thing and its associated information resource. >> >> >> >> ... And in most cases, one can use context to determine whether a >> statement concerns the thing or the information resource. In those cases >> where you can't, "URLs in Data Primer" suggests some mechanisms to mitigate >> such confusion [6][7]. >> >> >> >> I think that in our SDW WG discussion we have concluded that we _are_ >> content to use "indirect identification" - e.g. that we use URIs that >> conflate the thing and document resource. >> >> >> >> Please can we confirm this? Assuming that indirect identification is >> "approved" as best practice, then it seems prudent to add a note to the BP >> document saying "don't worry about distinguishing between thing and >> resource; indirect identification is fine" (etc.) >> >> >> >> Thanks, Jeremy >> >> >> >> [1]: http://w3c.github.io/sdw/bp/#globally-unique-ids >> >> [2]: https://www.w3.org/TR/webarch/#pr-uri-collision >> >> [2a]: https://www.w3.org/TR/webarch/#URI-collision >> >> [3]: https://www.w3.org/2001/tag/group/track/issues/14 >> >> [4]: https://www.w3.org/TR/urls-in-data/#publishing-data >> >> [5]: https://www.w3.org/TR/webarch/#indirect-identification >> >> [6]: https://www.w3.org/TR/urls-in-data/#documenting-properties >> >> [7]: https://www.w3.org/TR/urls-in-data/#authoring-specifications >> >> >> >> > -- Phil Archer W3C Data Activity Lead http://www.w3.org/2013/data/ http://philarcher.org +44 (0)7887 767755 @philarcher1
Received on Wednesday, 24 August 2016 08:23:51 UTC