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Re: ISSUE-120: Ambiguous Situation with nested @rel where inner @rel is neither CURIE nor link type

From: Manu Sporny <msporny@digitalbazaar.com>
Date: Sat, 10 May 2008 17:47:28 -0400
Message-ID: <482617F0.2060404@digitalbazaar.com>
To: public-rdf-in-xhtml-tf@w3.org

Ben Adida wrote:
> Manu Sporny wrote:
>> However, I also see specifying:
>>
>> rel=""
>>
>> as very different from specifying
>>
>> rel="foobarrel"
> 
> I would find it very confusing if those two cases would cause a triple
> "from above" to complete differently.

I didn't explain that very well... here's what I meant:

As an XHTML author, I would be surprised to find that inserting a
rel="foobarrel" would cause my chained triples to break. Most likely,
somebody taught me the trick that if I inserted:

rel=""

it would cause my chained triples to stop chaining. So, I'd be expecting
that... what I wouldn't expect is that doing something like:

rel="met"

would do the same thing. The reason being that when I wrote rel="met",
my brain was in the mode of writing Microformats, not RDFa. I wouldn't
expect my "Microformat markup" to affect my "RDFa markup".

I realize that when you think it through, it's logical - but I wouldn't
expect regular XHTML authors to grok it at first. Mostly because
about="" works differently, as does href="" and resource="". rel="" is
the only thing that I can see where it means "do not generate anything
further".

In other words, by rel="met" merely existing on the page, it halts
chaining. Usually triples are not generated because of the absence of an
attribute, not because one exists.

However, I do concede that the argument above is a bit pedantic and
assumes a certain train of thought that others may not follow.

> There's not other situation where that happens in RDFa: triple structure
> is affected by the *presence* of attributes, never by their specific
> value. Sure, a triple might disappear if @rel goes from valid to invalid
> CURIE, but the *other* triples whose predicate are specified elsewhere
> are not affected.

So, what I'm hearing both you and Mark say is that:

1. rel="" and rel="foobarrel" mean the same thing as far as the RDFa
   parser is concerned.
2. rel="" means something different than if @rel didn't exist at
   all on the element.

Is that a fair statement?

I'm afraid that #2 will be lost on most XHTML authors... but then again
we are talking about what will probably be a rarely used feature of
chaining.

We also don't specify this chain-halting feature anywhere in the Syntax
Document or the Primer, do we?

-- manu

-- 
Manu Sporny
President/CEO - Digital Bazaar, Inc.
blog: DB Launches Medical Record Sales Service with Shepherd Medical
http://blog.digitalbazaar.com/2008/02/24/health2trade/
Received on Saturday, 10 May 2008 21:49:06 GMT

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