CC

CC licenses have been represented three ways from the beginning. There's the legal text, the human readable "deed", and the machine readable RDF. If the legal text is what a lawyer would look at to understand the license, the RDF is what software would look like to understand it in a coarse grained fashion. It expressed the licenses in terms of permissions, requirements, and prohibitions, and contained pointers to things like translations, legal text, and version information.

For example, CC BY 4.0 has the following assertions:

  <cc:License rdf:about="http://creativecommons.org/licenses/by/4.0/">
    <cc:requires rdf:resource="http://creativecommons.org/ns#Notice"/>
    <cc:requires rdf:resource="http://creativecommons.org/ns#Attribution"/>
   <cc:permits rdf:resource="http://creativecommons.org/ns#Reproduction"/>
    <cc:permits rdf:resource="http://creativecommons.org/ns#Distribution"/>
    <cc:permits rdf:resource="http://creativecommons.org/ns#DerivativeWorks"/>
  </cc:License>

So CC BY 4.0 permits Reproduction, Distribution, and Derivative Works. Exercising those permissions requires Notice (identifying that you're using the work under the license) and Attribution (the original creator information).

This approach laid the groundwork for a lot of interesting possibilities: guidance on combining works, search with re-use in mind, and (later) easy attribution of works.