Re: RDFa and Microformats

Hi Toby,

I think you've missed the point.

If we have this:

  <span
    class="p1" content="v1"
    property="p2">v2</span>

How does the RDFa parser know that @content was added for use in a
Microformat, rather than for use in RDFa?

You can argue that you wouldn't do this, and that you'd advise people
to add extra elements to make things clear, but how do you absolutely
ensure against it?

This kind of pollution is exactly the problem that Microformats has
been unable to solve, and exactly the kind of problem that we put a
lot of energy into solving in RDFa.

To illustrate the issue, say I create a Microformat using your
technique, as follows:

  <span class="p1" content="v1">v2</span>

Your argument is that at the moment I don't have any RDFa. My argument
is that I do, because I have the @content attribute. Watch what
happens if I now try to add the following RDFa to that element:

  <span property="p2">v2</span>

The resulting mark-up is this:

  <span
    class="p1" content="v1"
    property="p2">v2</span>

but your Microformat-use of @content has messed up my RDFa-use of
@property. I.e., instead of:

  <> p2 "v2" .

we have:

  <> p2 "v1" .

We went to a *lot* of trouble to ensure this kind of thing didn't
happen. You'll see that in nearly all cases, Microformats patterns can
happily co-exist with RDFa, and that the addition or removal of
attributes from one does *not* cause problems with the other.

The proposal that you and Martin have here would fundamentally alter that.

Regards,

Mark

On Mon, Sep 15, 2008 at 12:28 PM, Toby A Inkster <tai@g5n.co.uk> wrote:
> On 15 Sep 2008, at 12:06, Mark Birbeck wrote:
>
>> However, if you now add a @content value that is tied to some other
>> property -- in Martin's example, @class -- then we have a similiar
>> situation to our previous one; how does the RDFa parser know that
>> @content is being used in a Microformatty-way, and not an RDFa-way:
>>
>>  <span
>>    class="dtstart" content="2008-06-28T21:00:00"
>>    property="foaf:name">Toby A Inkster</span>
>>
>> Your name is now a date, in the RDFa parser.
>
>
> This is not a problem of syntax, but just a problem of trying to do
> something silly. In short, the problems with the code you posted above have
> nothing to do with microformats. If you remove the 'class="dtstart"' - the
> only microformat class in the code - the problem still exists. The same
> problem would occur in a pure microformats or pure RDFa approach:
>
>        <abbr title="2008-06-28T21:00:00"
>        class="dtstart fn">Toby A Inkster</abbr>
>
>        <span content="2008-06-28T21:00:00"
>        property="c:dtstart foaf:name">Toby A Inkster</span>
>
> And is easily solved by adding a second element:
>
>        <span class="dtstart" content="2008-06-28T21:00:00">
>          <span property="foaf:name">Toby A Inkster</span>
>        </span>
>
>> Using the new attributes for something other than what they were
>> intended for, takes us right back to the situation we're trying to
>> escape from.
>
> The reason using @content to provide data values for Microformats is better
> than using @property plus @content, is that the use of @content alone does
> not create a triple in the RDFa processing model. So a <span
> class="dtstart"> with @content (and no RDFa-specific properties) will not
> create additional misleading triples in the RDFa processing model.
>
> --
> Toby A Inkster
> <mailto:mail@tobyinkster.co.uk>
> <http://tobyinkster.co.uk>
>
>
>
>



-- 
Mark Birbeck, webBackplane

mark.birbeck@webBackplane.com

http://webBackplane.com/mark-birbeck

webBackplane is a trading name of Backplane Ltd. (company number
05972288, registered office: 2nd Floor, 69/85 Tabernacle Street,
London, EC2A 4RR)

Received on Monday, 15 September 2008 12:17:01 UTC