Common Tag LogoAs strong believers in the semantic tagging (we wrote about it here and here), we are happy to announce that today one big  step toward realization of the idea is made.

Faviki is involved in the development of the  new open tagging format – Common Tag, together with AdaptiveBlue, DERI (NUI Galway), Freebase, Yahoo!, Zemanta, and Zigtag. This is the first time that this number of web companies have stepped together from day one to introduce a tagging standard.

People use tags to organize, share and discover content on the Web. However, in the absence of a common tagging format, the benefits of tagging have been limited. Individual things like New York City are often represented by multiple tags (like “nyc”, “new_york_city”, and “newyork”), making it difficult to organize related content; and it is not always clear what a particular tag represents – does the tag “orange” represent the fruit or the color?

The Common Tag format was developed to address the current shortcomings of tagging and help everyone, including end users, publishers, and developers get more out of Web content. It is an outcome of an effort to develop the easiest way to let publishers get more out of their content by semantically marking it up.

Common Tag format is based on RDFa, a standard mechanism for placing structured content within HTML documents. The format uses the URIs of concepts defined on the Web as a way of anchoring the meaning of Tag objects. Common concepts can be found, among others, in two big databases of structured content (or controlled vocabularies, as librarians call it) – Freebase and DBpedia.

Common Tag is based on a small vocabulary defining:

  • A class Tag, which holds the metadata provided by a Common Tag for a specific Resource.
  • Two properties:
    • tagged (connects a document to the Tag)
    • means (connects the Tag to the concept’s URI)

There are also few subclasses and optional properties, you can have a look at the whole specification. Also, developers may feel free to make use of RDFa’s flexibility to extend the expressiveness of the Common Tag format.

An example of two tags indicating that the document is about Twitter (DBpedia URI) and Web 2.0 (Freebase URI):

<body xmlns:ctag="http://commontag.org/ns#" rel="ctag:tagged">
    <span typeof="ctag:Tag"
              rel="ctag:means" resource="http://dbpedia/resource/Twitter" />

    <span typeof="ctag:Tag"
              rel="ctag:means" resource="http://rdf.freebase.com/ns/en/web_2_0" />
</body>

Faviki has implemented the Common Tag format (check out the extracted RDFa from Faviki Semantic Web topic page), and we hope that our users will benefit from it, as more publishers, developers and end users join in supporting the Common Tag format.

http://dbpedia/resource/Twitter
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