Introduction to RDFa II

by Mark Birbeck

10 Reader Comments

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  1. It seems that RDFa is an HTML upgrade from a simple object to a language. Up until now an HTML tag would just state :“This is a link” or “This is an image”. Now, with RDFa, every object tell a whole story: “This is a link about.. that was created on..”

    This will probably change search engines results dramatically. No more out dated articles or images, and much better mapping of the web.

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  2. It seems like RDFa is missing some consistency:

    href: a link betwen two documents<br /> imghref: the license of the linked element
    [rel=license][about]: the license of the linked element

    Seems confusing. What’s wrong with img@about?

    Also:

      <span property=“dc:created” c > – this document was created on 1 April 2009
      <img property=“dc:created” c > – this image was created on 1 April 2009

    It’s hard enough getting users (e.g. content editors) to use semantic markup. Confusing and contradictory semantic markup? Forget about it. Is there a saving grace that I’m missing?

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  3. Comment preview does not accurately preview comments. My apologies for the above formatting.

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  4. First of all, great set of intro articles! Though I am confused on one example (I even tried it).

    Note that the reference to each license is still a clickable link, so from a user’s perspective, nothing changes when we add @about to an anchor…

    Unless I am completely missing something here, it completely changes—there is no longer a link to the slide! Now the slide title links to the license… users will definitely notice that—again I might be missing something here.

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  5. That confused me, too, at first. I think the author intends the second <a> element (the one with the link to the license) to follow the first (the one with the link to the slides), not replace it. Confusing, since in the other examples the RDFa-ed version replaces the original.

    Still, overall a very informative and clearly written article.

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  6. inoni and somerain

    Sorry for the delay in getting back to you, but @somerain is exactly right—the problem with the mark-up is that we have extra code that is to be inserted, but in all of my previous snippets I’m showing how the mark-up evolves.

    I’ll see if that part can be rephrased a bit to make it clearer, and apologies for the confusion.

    Oh, and many thanks for taking the trouble to point this out!

    Mark

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  7. I understand that you can’t have multiple properties in attributes because attributes must be unique. It seems logical, therefore, to break it out into a big ol’ structure of tags, as illustrated. This makes sense in my mind as we are representing the data both to humans in the standard HTML and to machines in the RDFa additional markup.

    So I guess what seems weird to me is the ability to provide extra information only to machines by using the property/content combination. Shouldn’t that information also be being represented visually? And if it’s perfectly OK to hide potentially useful information from the visual consumers of this data, why is there no neat way to do it for more than one property? (I’m presuming the only way to provide multiple properties only to machines is to include empty spans or similar tags with the information in the attributes.)

    Having got my blustering confusion out of the way, thanks for these articles – I’m finding them very interesting and useful.

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  8. Firstly thanks for a pair of great articles.  RDFa is entirely new to me but having read both articles carefully I think I now have a grasp of the potential power of this level of markup.  It’s seems common sense to be able to apply attributes to specific elements of a page rather than to the document as a whole. The final @about example in the article brings it all together nicely showing the power and neatness of RDFa used in this way.  It is clear that this will allow both for better browser use of data – I like the example of search results / lists pages where the organizing of data in this way makes perfect sense – and also potential benefit for Search Engines to enhance their results.  With Google only just beginning to make use of RDFa it will be interesting to see how it’s use propagates.  It will also be interesting to see how Google (and the others Search Engines) handle the inevitable attempts to abuse the power of RDFa if it becomes an important part of the ranking algorithms.

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  9. I’m all for semantic markup, but I agree with what a couple of others have posted in this discussion; how are we going to get content editors to apply semantic markup to what they write? Currently there are some great WYSIWYG editors out there that transform standard text to HTML – now we need some smart cookie to develop the next generation of editor that transforms standard text to apply RFDa markup to what people write. Otherwise I see a big chasm in the adoption of this markup.

    Also, who is going to decide on which standard to use? “RFDa vs Microformats”:http://www.kelpdesign.com/tech-talk/rdfa-vs-microformats/ there are many developers already using Microformats, but I’m hoping that RFDa will become the preferred choice using XML namespaces to create a scalable form of markup. Will the development community or standards community win out?

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  10. Really clever, but come on, like most people say, how are we going to get an ordinary user to use this? How horrible is this syntax to learn? How many levels of inconsistencies and wierdness can we build on just to bow down to the XML/HTML altar?

    Name or Property – Ugh!
    href meaning different things depending on it’s element? – BIFF!, OW!
    More horrible xmlns syntax to learn? – Arrgh!!!
    Massive maintenance of the symantic ns register – No!!!

    Is this where XML finally jumps the shark? How long before we have to admit that every problem cannot be fixed with the XML hammer?

    Is it time to evolve?

    (Throws bomb – runs!) ;-)

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