W3C home > Mailing lists > Public > whatwg@whatwg.org > August 2007

[whatwg] Where did the "rev" attribute go?

From: Ian Hickson <ian@hixie.ch>
Date: Wed, 8 Aug 2007 04:15:31 +0000 (UTC)
Message-ID: <Pine.LNX.4.64.0708080355300.9521@dhalsim.dreamhost.com>

This e-mail consists of replies to a few e-mails on the subject of links 
and link relationship types. No changes were made to the spec in response 
to these e-mails; if you reply, please indicate if you think something 
needs to change in the spec. Thanks!

On Sat, 8 Jul 2006, Charles Iliya Krempeaux wrote:
> 
> But, if the intent [of removing 'rev'] to really get rid of confusion 
> then....  There's actually 2 things I noticed confuse people.
> 
> #1: That the label you pick for the "rel" (or "rev") needs to be a noun.  
> (I do understand why... at least I think I do... so that you can use the 
> same label in the "class" attribute.  But it makes things difficult for 
> some people.)

As others noted, the label you should pick for "rel" should be taken from 
a specific set of labels defined in a specification (either HTML4, or 
HTML5, or a Microformat spec, or some other extension specification). So 
the "noun" aspect isn't a source of confusion as far as I can tell. It may 
be that people don't know you shouldn't just arbitrarily make up now 
names, though.


> #2: That "rel" (and "rev") represent a relation between the two.  Often 
> people seem to want to "classify" what's at the end of the "href".  
> (Instead of specifying a relation.)  Perhaps a new attribute is needed.  
> Perhaps "hrefclass".

"class" on an <a> element can be used for this, IMHO.


On Tue, 11 Jul 2006, Charles Iliya Krempeaux wrote:
> 
> Let's say in a page, I have the following HTML code...
> 
> <li class="xoxo shows">
> <li><a rel="show" href="http://show.example.com/">Example IPTV
> Show</a></li>
> <li><a rel="show" href="http://show2.example.com/">Another Example IPTV
> Show</a></li>
> </li>
> 
> The semantics here are....  The class-xoxo (on the <li>) says that I'm 
> giving a list here.

I assume you meant to use an <ol> on the outside, not an <li>. And in that 
case, it's the <ol> that says that you're giving a list, the xoxo class 
isn't necesarry to give the "list" semantic.


> And the class-shows says this thing is/has "shows". (So basically, I'm 
> listing shows.)

This isn't a strong semantic (a random person who doesn't know you 
wouldn't necessarily know that's what your class meant), but it can be a 
convention you use within a particular community, sure.


> The rel-show inside the "list of shows", says what's at the end of the 
> "href" is a "show" for the list of "shows".

You could easily use "class" on the <a> element for this, without risking 
a clash with a future value introduced in (say) HTML6 for slideshow links. 
It would be as solid, semantically.

If you wanted to go further, you'd have to define a specification for your 
rel or class "show" value. Your specification could then include the rest 
of your description:

> So,... if you go to the URL in the "href", you get a whole HTML page 
> with all sort of stuff in there.  But what is the "show"?  The whole 
> page?  Just part of it?
> 
> Well, I then search the page for class-show.  (I look for something 
> inside the page with a class with the same token/name use in the "rel" 
> that linked there.)
> 
> If I find (just) one, then great, that's probably what I want to 
> concentrate on.  (The other parts of the page are probably irrelevent.)  
> If not, I'll probably have to concentrate on the whole page.
> 
> (This is the idea of opaque semantics that I was talking about before.)
> 
> Does that clear it up?
> 
> (This is what I imagined the developers of these things originally 
> thought up.)


> I suggested "hrefclass" because we already have things like... "lang" 
> and "hreflang".  It just seemed to follow the same style.  (Since this 
> seems to be just like the "class" attribute, expect we are applying it 
> to what is at the end of the "href"... so "hrefclass".)

I don't really understand why you can't just apply it to the link itself 
(i.e. use "class").


On Tue, 11 Jul 2006, Charles Iliya Krempeaux wrote:
> 
> Perhaps it's a poor example.  But what I've gotten from the specs is 
> that the "rel" attribute can be used in this way.

Could you check the HTML5 spec and let me know if it can still be 
interpreted this way?


> For an example that's gained some popularity, look at hCard. 
> http://microformats.org/wiki/hcard
> 
> People wanted to semantically denote "contact info".  So they choose a 
> set of class names to use (to do this) and some rules about them.
> 
> Creating the standard is a somewhat arbitrury process.  And requires 
> humans to do it.
> 
> Although with opaque semantics, like the "rel" name matching the "class" 
> name, you don't need a human intervention to parse much of it.
> 
> Does what I'm saying make sense?  Or should I explain it more?

I'm not convinced there's really a use case for making this automated to 
the level that you describe. It seems best to stick to having 
specifications for the cases that actually have uses.


> Alot of this is done for the benefit of machines (like browsers, 
> spiders, search engines, etc).

Right now, everything is done for the benefit of humans. The machines are 
just tools.


> But getting back to one things you said... it is NOT always the case 
> that you can "grab" something with an "id".  Sometimes using "class" 
> works better.
> 
> For example, consider if I wrote an article.  And, in the HTML for that 
> article, I mark certain parts of it as being part of a "summary" for it. 
> For example....
> 
> <p>
> <span class="summary">Blah blah blah.  Blah blah blah blah.  Blah blah
> blah blah.</span> Blah blah.
> </p>
> <p>
> Blah blah blah blah blah.  Blah blah blah blah.  Blah blah blah blah.
> Blah blah.  <span class="summary">Blah blah blah.</span>
> </p>
> <p>
> Blah blah blah.  Blah blah blah blah.  Blah blah blah blah. Blah blah.
> </p>
> 
> How would I grab that with an "id".
> 
> The class-summary's in there let me get at the summary that spread out 
> in multiple fragments.

What if the class isn't there? Why is the class different than the ID?


> Just one other example for good measure.  Consider this code...
> 
> <p>
> I am <a href="http://changelog.ca/">Charles Iliya Krempeaux</a>.
> </p>
> 
> As a human you can understand what that means.  You know it is a 
> statement. You know "Charles Iliya Krempeaux" is a name.  You know that 
> " http://changelog.ca/" is the site for "Charles Iliya Krempeaux".
> 
> But a machines does not know that.  It cannot figure that out.
> 
> That's where some "semantic salt" can be helpful.  hCard's let us add a 
> little semantics to make it so machines can figure out the "name" part 
> of it too.
> 
> So, if I were add an hCard I'd get...
> 
> <p>
> I am <a class="vcard fn url" href="http://changelog.ca/">Charles Iliya
> Krempeaux</a>.
> </p>
> 
> (The class-vcard, class-fn, and class-url are all part of hCard.)
> 
> With just that, machines now know that "Charles Iliya Krempeaux" is a 
> name. And "http://changelog.ca" is the site for "Charles Iliya 
> Krempeaux".
>
> I could even add more semantics....
> 
> <p>
> I am <a class="vcard fn url" href="http://changelog.ca/"><span
> class="given-name">Charles</span> <span class="additional-name">Iliya</span>
> <span class="family-name">Krempeaux</span></a>.
> </p>
> 
> Now, not only does it know that "Charles Iliya Krempeaux" is a name.  
> But it also knows that "Charles" is the person's "given name".  That 
> "Iliya" is that person's "additional name".  And that "Krempeaux" is 
> that person's "family name".
> 
> (If you are coming from an XML point-of-view.  Using the class names for 
> semantics is almost like entangling XML within HTML.  If that makes 
> sense.)

With you so far... But so what? As you say, this all works. Why do we need 
a generic mechanism? The only reason the computer "knows" that Krempeaux 
is your family name is because someone wrote a spec for class=family-name. 
It's not automatic, how can it be?

-- 
Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'
Received on Tuesday, 7 August 2007 21:15:31 UTC

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