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Re: an issue we need to address - bad @rel in the middle of a chain.

From: Mark Birbeck <mark.birbeck@x-port.net>
Date: Fri, 9 May 2008 08:57:36 +0100
Message-ID: <a707f8300805090057i55cbe866p4f8b4430a9523478@mail.gmail.com>
To: "Ben Adida" <ben@adida.net>
Cc: RDFa <public-rdf-in-xhtml-tf@w3.org>

Hi Ben,

I'm still at XTech so I don't have time to check this completely...but
just a few points.

This is the kind of issue I was considering when I used the wording
"act is if it wasn't there" in relation to @rel values. The scenario I
was trying to protect against was this one:

  <div about="" rel="dc:creator">
    <img rel="myfoobarrel foaf:img" href="ben.jpg" />

My wording was intended to allow 'myfoobarrel' to be silently ignored,
in such a way that 'foaf:img' was still processed, i.e., it acts like

  <div about="" rel="dc:creator">
    <img rel="foaf:img" href="ben.jpg" />

Your example is much the same, and should have the same effect as this:

  <div about="" rel="dc:creator">
    <img rel="" href="ben.jpg" />

I.e., the second statements have 'no effect'.

Now...since I was asked to change the wording to be 'stricter' I'm not
sure if I have lost the effect I was trying to achieve. I'll check
later, but if anyone else wants to take a look before I get a chance
to, I thought it worth providing the background info.



2008/5/9 Ben Adida <ben@adida.net>:
>  Hi all,
>  In a discussion today, Shane and I uncovered an edge case for which we have
> no test case. I think the spec says something about this edge case, and that
> the outcome is wrong. Shane thinks the spec is ambiguous. So, in either
> case, we need to clarify the situation.
>  Here's the markup that we believe is ambiguous:
>  <div about="" rel="dc:creator">
>    <img rel="myfoobarrel" href="ben.jpg" />
>  </div>
>  The question here is: does <ben.jpg> complete dc:creator, because
> myfoobarrel is neither a CURIE nor a link type? In other words, do we get
> the following triple:
>   <> dc:creator <ben.jpg> .
>  ?
>  My interpretation of the spec is that rel="myfoobarrel" is completely
> ignored, meaning that the triple completion behaves as if there was no @rel
> on the img, which means that <ben.jpg> indeed completes dc:creator. And I
> think that's a bad outcome.
>  Instead, I think the *presence* of @rel, no matter what it contains, should
> cause completion of the incomplete triples. Then, once the triples are
> completed, the *contents* of the @rel are considered for new triple
> creation.
>  Consider what would happen if you had a different @rel:
>  <div about="" rel="dc:creator">
>    <img rel="foaf:img" href="ben.jpg" />
>  </div>
>  which would then yield:
>   <> dc:creator _:bnode1 .
>   _:bnode1 foaf:img <ben.jpg> .
>  Changing the @rel value on img should certainly kill the second triple, but
> I don't see why it should change the first triple at all.
>  Thoughts?
>  -Ben
>  PS: adding this as an issue as soon as the email shows up in the archive.

 Mark Birbeck

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Received on Friday, 9 May 2008 07:58:18 UTC

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