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Subject: RE: [xri] FW: [link draft] Changing the model for links
Eran, thanks, this considerably relieves my angst about this issue. I really didn't want to be screwing up XRD architecture to accommodate this. =Drummond > -----Original Message----- > From: Eran Hammer-Lahav [mailto:eran@hueniverse.com] > Sent: Thursday, April 09, 2009 6:53 AM > To: Barnhill, William [USA]; Drummond Reed; xri@lists.oasis-open.org > Subject: Re: [xri] FW: [link draft] Changing the model for links > > I think at most, the link spec will call out the existing deployment of > alternate with a few other rels and deprecate this practice. If anyone > wants > to create combinations, they should just define new rel types. Even media > types based on +xml or +json still needs to be individually registered, so > that is the common practice here. > > Since <Rel> does not old multiple values, we do not have a way to express > this combination in XRD anyway. Separate <Rel>s are semantically > equivalent > to: > > Link: <a>; rel="a"; rel="b" > > Which does not fall under the HTML4 issue. > > So for us it is simply a matter of not being able to express this use case > (which is a good thing). > > EHL > > > On 4/9/09 5:02 AM, "Barnhill, William [USA]" <barnhill_william@bah.com> > wrote: > > > Could both camps be accommodated by saying that you have a special rel, > say > > '*' which ties together the rel preceding it and the rel following it > (e.g. > > rel="stylesheet * alternate")? > > > > Means extra work on those of us who having been using rel="x y" to > always mean > > 2 relationships, but at least it's distinguishable as one relationship > and you > > could check for presence of '*' relationship and not process special if > it > > didn't exist. Other benefit is that such relationships can be > represented as > > stylesheet*alternate xri subsegment. > > > > Someone would need to sell the HTML5 guys on the need though, but given > this > > may break several microformat mash-ups I wouldn't think it would be a > tough > > sell. > > > > =Bill.Barnhill > > > > > > -----Original Message----- > > From: Drummond Reed [mailto:drummond.reed@cordance.net] > > Sent: Thu 4/9/2009 1:59 AM > > To: 'Eran Hammer-Lahav'; xri@lists.oasis-open.org > > Subject: RE: [xri] FW: [link draft] Changing the model for links > > > > Man, this is a mess. It appears the whole root of the problem (which you > can > > see at http://www.w3.org/TR/html401/present/styles.html#specifying- > external) > > is that HTML 4 decided to create their own "keyword modifier" for values > of > > the rel= attribute in links. So you can insert the word "alternate" in > front > > of "stylesheet" (separated by a space, i.e., rel="alternate stylesheet") > to > > designate that it is an alternate stylesheet. > > > > > > > > By coming up with their own semantics for how two independent strings > modify > > each other as values of the rel attribute, they screwed up everyone else > who > > would simply want it to be able to contain multiple values. > > > > > > > > What were they THINKING???? It completely blows the regularity and > elegance > > of the architecture. > > > > > > > > I don't know about anyone else, but I feel they have set such a bad > > precedent here that I don't think we or anyone else should be obliged to > > follow it. I think we should stick to the rel attribute accepting > multiple > > space-delimited values, and just accept that if certain of those values > have > > a relationship to certain other of those values, that's application > > specific. > > > > > > > > Otherwise we'd end out completely screwing up the link model (and XRD > 1.0 > > architecture that is based on it) to accommodate somebody else's bad > > decision. > > > > > > > > I propose we make this the lead (and maybe only) topic on tomorrow's XRI > TC > > telecon because it's so important to get this feedback in now. > > > > > > > > =Drummond > > > > > > > > _____ > > > > From: Eran Hammer-Lahav [mailto:eran@hueniverse.com] > > Sent: Wednesday, April 08, 2009 8:39 AM > > To: Eran Hammer-Lahav; xri@lists.oasis-open.org > > Subject: Re: [xri] FW: [link draft] Changing the model for links > > > > > > > > I forgot to mention this discussion is taking place on the HTTP list > > ietf-http-wg@w3.org > > > > EHL > > > > > > On 4/8/09 8:22 AM, "Eran Hammer-Lahav" <eran@hueniverse.com> wrote: > > > > This will have significant impact on XRD. Please read. > > > > EHL > > > > > > ------ Forwarded Message > > > > From: Mark Nottingham <mnot@mnot.net> > > Date: Tue, 7 Apr 2009 16:21:34 -0700 > > To: <www-tag@w3.org> > > Subject: Fwd: [link draft] Changing the model for links > > > > > > > > > > > > > > Begin forwarded message: > > > >> Resent-From: ietf-http-wg@w3.org > >> From: Mark Nottingham <mnot@mnot.net> > >> Date: 8 April 2009 9:10:58 AM > >> To: HTTP Working Group <ietf-http-wg@w3.org> > >> Cc: Ian Hickson <ian@hixie.ch> > >> Subject: [link draft] Changing the model for links > >> Archived-At: > > <http://www.w3.org/mid/C1CD0848-13F0-4FCF-91FF-52126622C3B8@mnot.net > >>> > >> > >> I've been discussing the link draft with Ian Hickson, who points out > >> that in HTML4, there's a difference between > >> > >> <link rel="stylesheet" href="a"/> > >> <link rel="stylesheet alternate" href="a"/> > >> > >> and > >> > >> <link rel="stylesheet alternate" href="a/> > >> > >> (see <http://www.w3.org/TR/html401/present/styles.html#specifying- > external > > > >>> for the background of why these are different) > >> > >> In the current link draft, there isn't any way to express the > >> difference between these; the underlying model is > >> > >> [ context ] ---[ relation type ]---> [ target ] > >> > >> where 'relation type' is singular. > >> > >> To accommodate this use, the model would need to be something like > >> > >> [ context ] ---[ list of relation types ]---> [ target ] > >> > >> noting that there may be more than one list of relation types > >> between any context and target. > >> > >> Personally, I think that it would be only in pathological cases that > >> it would be necessary to know the difference between the two (i.e., > >> real world Web pages will not point to a URI as both a stylesheet > >> and as an alternate for themselves, so it's safe to say that even > >> the first example above means that "a" is an alternate stylesheet). > >> > >> However, it is important for Link to interoperate well with HTML4. > >> Also, the HTML5 folks plan to use this model for other purposes > >> (e.g., "up up" to indicate a parent of a parent). > >> > >> The practical impact of making this change is that serialisations of > >> links won't be able to collapse multiple relation types between two > >> URIs into one link; they'll have to be separate to allow this > >> interpretation. > >> > >> So, for example, if you have link types ['w', 'x', 'y z'] between A > >> and B, it will have to be serialised as > >> > >> Link: <B>; rel="w" > >> Link: <B>; rel="x" > >> Link: <B>; rel="y z" > >> > >> in HTTP headers, NOT > >> > >> Link: <B>; rel="w x y z" > >> > >> because that's ambiguous. > >> > >> The alternative is to say that the 'stylesheet alternate' > >> combination isn't specific to how it's serialised, but is tied to > >> the occurrence of the links. I.e., when both relations are present > >> in links between the same resources, these special semantics take > >> affect. However, this does seem to directly conflict with the HTML4 > >> language (see link above), so I don't think doing so is viable. > >> > >> Comments? > >> > >> -- > >> Mark Nottingham http://www.mnot.net/ > >> > >> > > > > > > -- > > Mark Nottingham http://www.mnot.net/ > > > > > > > > > > > > ------ End of Forwarded Message > > > > > >
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