- From: Jason Douglas <jasondouglas@google.com>
- Date: Sat, 22 Oct 2011 10:18:40 -0700
- To: Manu Sporny <msporny@digitalbazaar.com>
- Cc: W3C Vocabularies <public-vocabs@w3.org>
- Message-ID: <CAEiKvUD6BwEOPtocj+=n=okHBaVbsXZKbNafVvSkR1RqM-w0-g@mail.gmail.com>
On Fri, Oct 21, 2011 at 7:16 PM, Manu Sporny <msporny@digitalbazaar.com>wrote: > On 10/21/2011 01:08 PM, Jason Douglas wrote: > >> There's a lot to like here. >> > > Glad to hear that. Jason, apologies for the late-joining on my part - but > are you actively involved with the Rich Snippets stuff at Google, or just > interested in it from a design perspective? I'll wait to follow-up on everything else on the new threads Guha is spinning off, but I figure I should still introduce myself here: I came to Google from the Metaweb acquisition and now, in addition to Freebase, my work includes parts of Google's infrastructure for processing structured markup. I also contributed bits and pieces to the initial schema.orgvocabularies. So I'm interested from all angles. :-) -jason However, the two biggest issues raised in >> the discussion at the workshop seem unaddressed / unacknowledged to me >> by this document: >> > > Just to clarify - the document was meant to be a quick and dirty > introduction - not a complete specification. So, there were many things that > were left unsaid/unexplained. > > > 1/ Why both property and rel? There was concern expressed that >> implementers wouldn't understand the difference (honestly, I'm not sure >> I do) and it wasn't made clear why having both is necessary. If the >> distinction is literal value vs. url, why not use value precedence (like >> itemprop in microdata)? >> > > You could say that the distinction is "literal value vs. URL", but that's a > bit of an over-generalization. @rel exists for a number of reasons: > > 1. It has always been the mechanism used in HTML to specify relevance > (aka: relationship information) to links on the Web. > 2. We found that often people want to create a link relationship and > express a literal value at the same time, on the same element. > Having @rel and @property allows them to do that without having > to change their document structure. > 3. The use was re-inforced in the Microformats community after > extensive study of usage patterns and it seems like people > were getting its usage correct. > 4. Creative Commons supports the usage of @rel and many of their > implementers get it. > > In the 3 years since RDFa 1.0 has been in the field, we see very little > abuse of @rel. In fact, we see far more examples of correct @rel usage in > RDFa 1.0 than we do incorrect usage. So, while I do understand the concern, > is there any publicly available study or data to back up the concern? > > The reason we didn't go with value precedence is for the reasons listed > above. Value precedence also doesn't work when you really want to express a > literal, but there just happens to be an @href on the element. We had > considered this during the design of RDFa 1.0, but found it to not be > adequate for the use cases we were considering for RDFa. > > Is the existence of @rel a deal-break for anyone? If so, why? > > > 2/ Layer-ability on existing markup. That's probably too abstract a >> label... basically, implementers have found the itemref feature of >> microdata to be useful in layering vocabulary on top of existing pages. >> > > I have a hard time believing this claim. I've found @itemref to be one of > the most difficult parts of Microdata to use, and have not really found it > to be that helpful in most documents. Do you have any numbers on the number > of documents that use @itemref, or the frequency in which it is used on the > Web? > > > For example, if the name of a product is in one part of the DOM tree, >> but it's properties are in an entirely different one, how do you combine >> them? >> > > Use @about. > > > If both the about URI and the markup >> with the about attribute have RDFa in them, how are those properties and >> types combined? >> > > Like this: > > <div about="#jason" typeof="schema:Person"> > <span property="schema:name">Jason Douglas</span> > ... other stuff about Jason ... > </div> > ... Lots and lots of HTML ... > <span about=#jason" property="schema:jobTitle">**Product Manager</span> > > Any time that you want to talk about the same subject again - you just use > the same @about value. Make sense? > > > -- manu > > -- > Manu Sporny (skype: msporny, twitter: manusporny) > Founder/CEO - Digital Bazaar, Inc. > blog: Standardizing Payment Links - Why Online Tipping has Failed > http://manu.sporny.org/2011/**payment-links/<http://manu.sporny.org/2011/payment-links/> > >
Received on Saturday, 22 October 2011 17:19:17 UTC