10. CC REL: The Creative Commons Rights Expression Language

摘要: RDF graphs can be expressed textually in various ways. One commonly used notation, RDF/XML, uses XML syntax. In RDF/XML the triple describing licensing of Lessig’s blog is denoted: desirable feature notation that it completely self-contained: all identifiers are fully qualified URLs. On other hand, extremely verbose, making cumbersome for people to read and write, especially if no shorthand conventions used. Even this simple example (verbose as is) a mechanism: second line description beginning xmlns:xhtml defines “xhtml:” an abbreviation http://www.w3.org/1999/ xhtml/vocab#, thus expressing license property its shorter form, xhtml:license, on fourth line. Since introduction RDF, Web Consortium has developed more compact alternative syntaxes graphs. For N3 syntax would denote above concisely:9 . We could also rewrite using RDF/XHTML above, defining: xhtml: http://www.w3.org/1999/xhtml/vocab#: @prefix xhtml:license The does not provide improved compactness or readability prefix only once course. N3, prefixes typically defined when they than once, express multiple properties taken from same vocabulary. because stricter parsing rules XML, there bit less flexibility: predicates shorthand, while subjects full URI. 2.2 CC’s Previous Recommendation: HTML Comments With first unveiling machine-readable licenses 2002, Creative Commons recommended publishers use properties. CC web site included (Notation 3) was designed readable RDF/XML. See http://www. w3.org/DesignIssues/Notation3.html.