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Simon Willison’s Weblog

Creative Commons copyright link

It’s great to see the Creative Commons getting an overwhelmingly positive reception—as Lessig says on his blog, ’Tis the season to be giving, and this will be a great gift to the Commons. If you haven’t seen their explanatory flash animation, Get Creative, you should really check it out.

That said, I have to admit I have a few reservations about the machine readable form of the CC licenses. The recommended way of including them in a page is RDF embedded in a comment, similar to Moveable Type’s Trackback system. This is fine for HTML documents (although it feels like a bit of a cludge) but is problematic when used with XHTML. Why? Because XHTML documents are XML documents, and the XML specification states that an XML processor may, but need not, make it possible for an application to retrieve the text of comments. The logical way of extracting Creative Commons information from an XHTML document would be to parse it with an XML processor, but it is likely that many processors will be unable to extract the comments (and even those with the ability to extract them will not treat them as XML, requiring a second run of the XML parser to extract information from the RDF). In practical terms this is unlikely to be a problem as regular expressions can be used instead, but from an idealogical point of view it leaves something of a bad taste in the mouth.

If I’m going to criticise the embedded RDF approach I should probably suggest an alternative. The HTML 4 specification describes a “Copyright” link type which is defined as follows:

Copyright
Refers to a copyright statement for the current document.

I suggest using a link element in the <head> section of a document which points to the Creative Commons license governing the page in question (or to an RDF document similar to that currently used by the embedded comments method). If you view source on your page you will see that I have done exactly that.

Posted 19th December 2002 at 12:41 am

This is Creative Commons copyright link by Simon Willison, posted on 19th December 2002.

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3 comments

  1. Funny, I was going to suggest exactly the same thing when I'd read halfway through your post, and hadn't yet noticed that you'd also suggested it.

    Lach - 19th December 2002 02:47 - #

  2. One of the few things I liked on the whole CC site was one of the "Cons" for embedding in an HTML comment: "Makes people queasy." I assume Aaron's pet Python parser doesn't mind RDF in a comment in (X)HTML, and that's all that matters, isn't it?

    Phil Ringnalda - 21st December 2002 03:57 - #

  3. For reference, the reason people don't put RDF or other well-formed XML into XHTML is because, as it stands today, it makes the XHTML invalid (won't validate to the XHTML DTD). When that issue is resolved, the technique for embedding other namespaces into XHTML will (should) also be provided.

    Ken MacLeod - 11th July 2003 15:42 - #

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