When you select a license from the Creative Commons License Chooser, you're provided with HTML to place in your page. That HTML contains metadata which allows software to understand that you've applied a license to your work.
What are metadata, RDF, and the Semantic Web?
Metadata is data about data. For example: title, creator, and licensing information. When you choose a license on our website, you get back some metadata (licensing information) encoded in RDF.
RDF (Resource Description Framework) is a framework for metadata. The basic structure of RDF is very simple. There are three parts:
- the subject: a thing, identified by its URL
- the predicate: the type of metadata (like title or creator), also identified by a URL
- the object: the value of this type of metadata (like "The Story of My Life" or 'a person named "John Q. Public"')
Together, these make RDF statements, which are expressed in a language called RDF/XML.
The Semantic Web is the part of the Web available in RDF. The idea behind the concept of the Semantic Web is that when enough pages carry this machine-processable metadata, developers can build tools that take advantage of it.
Among other things, RDF helps different programs talk to each other, reducing the need for users to copy information by hand. Imagine a world where everything had embedded RDF: When buying a plane ticket, for example, you could drag your flight itinerary onto your calendar program to add it to your calendar. You could drag a friend's top-ten songs list onto your music player, and it could try and obtain the songs for you automatically.
RDF can also be used to create more powerful search engines. Right now the only type of question you can ask a search engine is "What pages have these words in them?" When pages include RDF metadata, you will be able to ask more advanced questions like "What's the current temperature in California?" Programs can also use this information, like an alarm clock program that also displayed the current weather or a collage-making program that only used photos with permission.
Finally, metadata can be aggregated across the whole Web. A program could download all the top-ten song lists and, with the help of a pricing guide in RDF, calculate the cost of buying the most popular albums.
Metadata holds a lot of promise, but it won't be useful until people start adding it to their pages. Creative Commons hopes to help promote metadata by making it very easy for people to add metadata to their pages.
Why we have Creative Commons Metadata
In addition to making it easy for people to find the copyright licenses best for them, Creative Commons is working to provide simple RDF descriptions of these licenses. These descriptions will put the important points of the license in a way that makes it easy for machines to process and work from. Unlike Digital Rights Management (DRM) technology, which tries to restrict use of digital works, Creative Commons is providing ways to encourage permitted sharing and reuse of works.
If you run a search engine, you might use license metadata to highlight public domain and generously-licensed works. If you write a public file sharing server, you might offer to search the user's hard drive for works that allow distribution. If you write a magazine, you might use a CC-enabled search engine to find pictures of candy bars that you can legally include.
By standardizing a way to describe this information and providing large quantites of RDF to build on, we hope to encourage new and innovative ways to develop the commons. Of course, this metadata only provides a first approximation of the license, for information use. Users are encouraged to read the full license to make sure it meets their expectations.