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Re: @rel and @property symmetry

From: Shane McCarron <shane@aptest.com>
Date: Thu, 10 Nov 2011 17:25:54 -0600
To: Jeni Tennison <jeni@jenitennison.com>, RDFa WG <public-rdfa-wg@w3.org>
Message-ID: <ab0ea64b-9642-49b5-b8cb-3ae04586f971@email.android.com>
Great analysis. I am pretty sure I agree. I will have to look more closely when I have a whiteboard and no headache.
-- 
Sent from my Android phone with K-9 Mail. Please excuse my brevity.

Jeni Tennison <jeni@jenitennison.com> wrote:

Hi,

I noticed in the minutes of your meeting today that you talked a bit about symmetry between @rel and @property.

I did a write-up showing parallel microformats, microdata and RDFa markup recently [1] and without even trying (I didn't pick this case specifically, just selected an example from schema.org randomly) came up against the unwanted chaining issue that Michael Steidl raised last month [2]. The example was to create

[ a schema:Event ;
schema:url <nba-miami-philidelphia-game3.html> ;
schema:name " Miami Heat at Philadelphia 76ers - Game 3 (Home Game 1) " ; ]

with markup like:

<div about="_:event" vocab="http://schema.org/" typeof="Event">
<a rel="url" href="nba-miami-philidelphia-game3.html">
<span about="_:event">
NBA Eastern Conference First Round Playoff Tickets:
<span property="name"> Miami Heat at Philadelphia 76ers - Game 3 (Home Game 1) </span>
</span>
</a>
...
</div>

Note the use of the blank node named _:event in order to bypass the unwanted chaining; I couldn't think of another way of doing it without repeating content (does anyone else have another suggestion?).

So I'm really pleased to see the adoption of @property *without* chaining, which allows this to be rewritten as:

<div vocab="http://schema.org/" typeof="Event">
<a property="url" href="nba-miami-philidelphia-game3.html">
NBA Eastern Conference First Round Playoff Tickets:
<span property="name"> Miami Heat at Philadelphia 76ers - Game 3 (Home Game 1) </span>
</a>
...
</div>

This is a plea to not to make @property always chain: not chaining is useful, and it is a good thing to give a publisher an easy way to do it.

I also support not changing @rel behaviour, both for backwards-compatibility reasons and because although it's useful to have non-chaining behaviour, it is *also* useful sometimes to have chaining. I don't think the lack of symmetry is a problem if you think of @rel as an advanced variant of normal @property behaviour rather than them being synonyms.

Cheers,

Jeni

[1] http://www.w3.org/wiki/Mixing_HTML_Data_Formats#Mixing_Syntaxes
[2] http://lists.w3.org/Archives/Public/public-rdfa-wg/2011Oct/0018.html
-- 
Jeni Tennison
http://www.jenitennison.com
Received on Thursday, 10 November 2011 23:26:15 GMT

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