- From: Ivan Herman <ivan@w3.org>
- Date: Tue, 17 Nov 2009 17:03:03 +0100
- To: Niklas Lindström <lindstream@gmail.com>
- CC: Mark Birbeck <mark.birbeck@webbackplane.com>, Ben Adida <ben@adida.net>, RDFa <public-rdf-in-xhtml-tf@w3.org>
- Message-ID: <4B02C937.30109@w3.org>
Niklas Lindström wrote: > Ivan, Mark, > > but people are alredy doing it [1] [2] -- including the W3C [3]! > > [1] = <http://www.jenitennison.com/blog/node/133> > [2] = <http://www.holygoat.co.uk/projects/tags/> > [3] = <http://www.w3.org/TR/HTTP-in-RDF10/> > > So neither declaring it bad practise nor forbidding it syntactically > seems really proper to me.. > I think Shane's proposal, ie, that the document would say "should not do it" gives the right balance. I agree forbidding it is too much; the 'should not' is not bad practice, just a kind of a warning that people, well, should avoid doing this... My feeling is that this type of usage is (and should be:-) rare, and the gains vastly overweight the possible complications. Obviously, this is not a technical argument... Ivan > And as for "people knowing what they are doing", is that really enough > when introducing something that would drastically change the > interpreted values in @about/@typeof (when the protocol names have > been declared as prefixes "somewhere higher up"); and in a non-obvious > way for someone looking at just the URI:s? > > To do this just feels brittle to me. (And, I fear, would increase the > dislike of CURIEs/prefix mechanisms.) > > Of course, I also realise that not doing this, while introducing > "CURIE or URI-if-undefined-prefix" rules (where CURIE was the > precedent and "as URI" is new), may be confusing as well. Since it > would be very hard to distinguish between the syntax allowed in > @property and @rel, and the "plain URI only" attributes.. (The > attributes will have same *apparent* lexical space, but in some of > them, defined prefixes would have profound effects..) > > .. But I have no alternate suggestions either I'm afraid. Apart > perhaps from redesign/new syntax such as if "[...]" could be used to > expand prefixes everywhere, e.g. about="[foaf]Person", > property="[foaf]homepage".. But that's probably awkward. > > (.. Or just (ducks and covers) "skip CURIEs altogether and let XML > users use the old, ugly ENTITY mechanism for shortening". I sure > prefer using prefixes+CURIEs to replace that.. Not the least since in > HTML scenarios it would probably be a no-go anyway.) > > Best regards, > Niklas > > > > 2009/11/17 Ivan Herman <ivan@w3.org>: >> That is probably correct. It is also a very bad authoring practice... >> >> In more general terms, one could declare a number of strings as being >> off-limit for CURIE-s. But I am not sure it is worth the trouble in >> terms of usage. >> >> Ivan >> >> >> >> Niklas Lindström wrote: >>> Another point though. Isn't there a problem if prefixes are declared >>> for existing protocols? >>> >>> When prefixes are declared for e.g.: >>> >>> xmlns:http="http://www.w3.org/2006/http#" >>> xmlns:tag="http://example.org/tagging#" >>> >>> With the proposed rules ("unsafe CURIE or URI"), wouldn't these: >>> >>> about="http://example.org/me" >>> resource="tag:example.org,2009:item:1" >>> >>> be resolved against those prefixes (instead of as-is)? >>> >>> Best regards, >>> Niklas >>> >>> >>> 2009/11/16 Niklas Lindström <lindstream@gmail.com>: >>>> Ah, but indeed! Good elephant-hunting Mark! ;) It's quite comforting >>>> that RFC 3986 is so precise about these things. >>>> >>>> (I should have known that -- I now recall reading that very same rule >>>> a couple of months ago when investigating the legality of non-escaped >>>> colons in URI:s. Only remembered half of it apparently.) >>>> >>>> Best regards, >>>> Niklas >>>> >>>> >>>> 2009/11/16 Ivan Herman <ivan@w3.org>: >>>>> Pfew...:-) >>>>> >>>>> Ivan >>>>> >>>>> P.S. Mark-the-elephant-hunter:-) >>>>> >>>>> Mark Birbeck wrote: >>>>>> Hi Ivan/Niklas, >>>>>> >>>>>> 2009/11/16 Ivan Herman <ivan@w3.org>: >>>>>>> Hi Niklas, >>>>>>> >>>>>>> Niklas Lindström wrote: >>>>>>>>> So is there an elephant?:-) >>>>>>>> I haven't followed this discussion to closely, so I want to check if >>>>>>>> this the following is considered: >>>>>>>> >>>>>>>> This usage will "muddle the waters" in cases when the relative URI:s >>>>>>>> contain colon, and there is a prefix with the same name as the leading >>>>>>>> part before that, right? Concrete (but contrieved) example: >>>>>>>> >>>>>>>> Given: >>>>>>>> - base URI: <http://en.wikipedia.org/wiki/> >>>>>>>> - prefix Talk: <http://example.org/schema/talk#> >>>>>>>> >>>>>>>> When: >>>>>>>> @resource="Talk:Linked_Data" >>>>>>>> >>>>>>>> Then: >>>>>>>> - URI becomes < http://example.org/schema/talk#Linked_Data>, >>>>>>>> instead of <http://en.wikipedia.org/wiki/Talk:Linked_Data>, which is >>>>>>>> might be expected? >>>>>>>> >>>>>>> Hm. You may found the elephant:-) >>>>>>> >>>>>>> Yes, in this case one would indeed get the example.org URI. >>>>>>> >>>>>>> The question is: is this use case so strong as to nullify the advantages >>>>>>> of using CURIE-s in @about? Indeed, wikipedia uses such URI-s with ':' >>>>>>> quite a lot but the user can of course put full URI-s into the value of >>>>>>> @about... >>>>>>> >>>>>>> Thanks! >>>>>> Whoah...slow down. :) >>>>>> >>>>>> "Talk:Linked_Data" is not a relative path! >>>>>> >>>>>> Forget prefixes, CURIEs, whatever...even if those things did not >>>>>> exist, how would a URI processor know whether "Talk:" is a scheme or >>>>>> just part of a relative path? >>>>>> >>>>>> RFC 3986 [1] addresses this in the following way: >>>>>> >>>>>> A path segment that contains a colon character (e.g., "this:that") >>>>>> cannot be used as the >>>>>> first segment of a relative-path reference, as it would be mistaken >>>>>> for a scheme name. >>>>>> Such a segment must be preceded by a dot-segment (e.g., >>>>>> "./this:that") to make a >>>>>> relative-path reference. >>>>>> >>>>>> So, if people are using relative paths that contain colons, in the >>>>>> wild, then there's a problem, and that problem is completely >>>>>> independent of RDFa. >>>>>> >>>>>> Regards, >>>>>> >>>>>> Mark >>>>>> >>>>>> [1] <http://www.ietf.org/rfc/rfc3986.txt> >>>>>> >>>>>> -- >>>>>> Mark Birbeck, webBackplane >>>>>> >>>>>> mark.birbeck@webBackplane.com >>>>>> >>>>>> http://webBackplane.com/mark-birbeck >>>>>> >>>>>> webBackplane is a trading name of Backplane Ltd. (company number >>>>>> 05972288, registered office: 2nd Floor, 69/85 Tabernacle Street, >>>>>> London, EC2A 4RR) >>>>> -- >>>>> >>>>> Ivan Herman, W3C Semantic Web Activity Lead >>>>> Home: http://www.w3.org/People/Ivan/ >>>>> mobile: +31-641044153 >>>>> PGP Key: http://www.ivan-herman.net/pgpkey.html >>>>> FOAF: http://www.ivan-herman.net/foaf.rdf >>>>> >>>>> >> -- >> >> Ivan Herman, W3C Semantic Web Activity Lead >> Home: http://www.w3.org/People/Ivan/ >> mobile: +31-641044153 >> PGP Key: http://www.ivan-herman.net/pgpkey.html >> FOAF: http://www.ivan-herman.net/foaf.rdf >> >> -- Ivan Herman, W3C Semantic Web Activity Lead Home: http://www.w3.org/People/Ivan/ mobile: +31-641044153 PGP Key: http://www.ivan-herman.net/pgpkey.html FOAF: http://www.ivan-herman.net/foaf.rdf
Received on Tuesday, 17 November 2009 16:03:35 UTC