Difference between revisions of "CC0 Technical Overview"

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Revision as of 22:35, 14 April 2008

CC∅ provides a framework that enables people to

  • (a) ASSERT that a work is free of copyright as a matter of fact, for example, because the work is old enough to be in the public domain, or because the work is in a class not protected by copyright such as U.S. government works. Curators and publishers of public domain material may be well placed to make such an assertion.


  • (b) WAIVE all copyrights and related or neighboring interests that you have over a work. You can only do this if you hold the necessary rights for the work.

This page describes the metadata used to describe these two complementary paths along with suggestions for publishers who wish to use CC∅.


CC∅ introduces four new predicates in the Creative Commons namespace.

  • licenseOffer: The URI or (as generated by the beta CC∅ chooser) blank node bundling the details of a license offer or assertion. A license offer can contain information regarding the specific license URI (license), the actor (cc:assertedBy or cc:waivedBy, etc).
  • assertedBy: The URI of the actor asserting that a work is free of legal restrictions.
  • waivedBy: The URI of the actor (rights holder) waiving all legal rights to a work.
  • assertionBasis: The URI or literal text description for the basis of the license assertion.

Additionally, the beta chooser uses two URIs to denote possible basis for asserting CC∅ over a work:

  • us_1923: Works created before 1923 in the US are in the public domain; this URI completes the (<work>, cc:assertionBasis, <reason>) triple.
  • us_govt: Works created by the US government are in the public domain; this URI completes the (<work>, cc:assertionBasis, <reason>) triple.


The CC∅ application returns HTML with embedded metadata describing the role the user has selected, along with any additional metadata provided.

Waiving Rights

For example, a user waiving all rights to a work:

<p xmlns:cc="http://creativecommons.org/ns#"
        xmlns:dc="http://purl.org/dc/elements/1.1/" about="http://example.org/~auser/brilliance" rel="cc:licenseOffer">
<a rel="license"
   href="http://labs.creativecommons.org/licenses/zero-waive/1.0/us/" style="text-decoration:none;">
   <img src="http://labs.creativecommons.org/zero/images/88x31/cc-zero.png" border="0" alt="CC0" /></a>
<br/>To the extent possible under law, <a rel="cc:waivedBy" href="http://example.com/~auser">
<span about="http://example.com/~auser" property="dc:title">A. User</span></a> has <a rel="license"
all copyright, moral rights, database rights, and any other rights that 
might be asserted over <a href="http://example.org/~auser/brilliance"><span about="http://example.org/~auser/brilliance" property="dc:title">Brilliance Described</span></a>.

Described in N3, the triples encoded in the above HTML are:

<http://example.org/~auser/brilliance> <http://creativecommons.org/ns#licenseOffer> _:n0 .
<http://example.org/~auser/brilliance> <http://purl.org/dc/elements/1.1/title> "Brilliance Described" .

_:n0 <http://www.w3.org/1999/xhtml/vocab#license> <http://labs.creativecommons.org/licenses/zero-waive/1.0/us/> .
_:n0 <http://creativecommons.org/ns#waivedBy> <http://example.com/~auser> .

<http://example.com/~auser> <http://purl.org/dc/elements/1.1/title> "A. User" .

As you can see, this metadata makes statements about both the work and the person waiving their rights over the work.

Asserting a Work's Freedom

Alternately, a user asserting that a work is free of legal restrictions:

<p xmlns:cc="http://creativecommons.org/ns#"
        about="http://example.com/~auser/brilliance" rel="cc:licenseOffer">
  <a rel="license"
     href="http://labs.creativecommons.org/licenses/zero-assert/1.0/us/" style="text-decoration:none;">
     <img src="http://labs.creativecommons.org/zero/images/88x31/cc-zero.png" border="0" alt="" />
  <br/><a rel="cc:assertedBy" href="http://example.com/~fbar">
<span about="http://example.com/~fbar" property="dc:title">F. Bar</span></a> asserts <a href="http://example.com/~auser/brilliance"><span about="http://example.com/~auser/brilliance" property="dc:title">Brilliance Described</span></a>  is <a rel="license"
    of any copyrights</a>; <a href="http://creativecommons.org/ns#us_1923" rel="cc:assertionBasis">the work was created in the U.S. before 1923</a></p>

Described in N3, the triples encoded in the HTML above are:

<http://example.com/~auser/brilliance> <http://creativecommons.org/ns#licenseOffer> _:n0 .
<http://example.com/~auser/brilliance> <http://purl.org/dc/elements/1.1/title> "Brilliance Described" .

_:n0 <http://www.w3.org/1999/xhtml/vocab#license> <http://labs.creativecommons.org/licenses/zero-assert/1.0/us/> .
_:n0 <http://creativecommons.org/ns#assertedBy> <http://example.com/~fbar> .
_:n0 <http://creativecommons.org/ns#assertionBasis> <http://creativecommons.org/ns#us_1923> .

<http://example.com/~fbar> <http://purl.org/dc/elements/1.1/title> "F. Bar" .


Creative Commons recommends marking works published under CC∅ with embedded metadata. Metadata allows search engines and web software to find structured information about pages. The minimal recommended case is specifying CC∅ as the license. Note CC∅ is not a license but provides similar information regarding re-use rights. Therefore we reuse the existing, supported infrastructure.

For example:

All legal rights to this page have <a rel="license" 
href="http://labs.creativecommons.org/licenses/zero/1.0/">been waived</a>.

Additional metadata may be specified using the assertedBy or waivedBy predicates. Each specifies a URI; publishers are encouraged to provide additional metadata about the actor at that location.