With the help of Kingsley, Uldis and I have been looking at how SIOC can be used to link the content that a single person posts to a number of community sites. The picture below shows an example of stuff that I’ve created on Flickr, YouTube, etc. through my various user identities on those sites (these match some SIOC types that we want to add to a separate module). We can also say that each Web 2.0 content item is a user-contributed post, with some attached or embedded content (e.g. a file or maybe just some metadata). This is part of a new discussion on the sioc-dev mailing list, and we’d value your contributions.
Edit: The inner layer is a person (semantically described in FOAF), the next layer is their user accounts (described in FOAF, SIOC) and the outer layer is the posted content – text, files, associated metadata – on community sites (again described using SIOC).
Another interesting application is being able to “view everyone’s contributions to the Social Web” with SIOC. At the moment, a lot of content is being created on Web 2.0 sites (events, bookmarks, videos, etc.) and this content is being annotated and commented on by others. If you consider such content to be the starting point of a discussion about the content, and the content being created is done so in a forum linked to a user or topic, then SIOC is a natural choice to describe metadata about this content. The SIOC ontology can be extended to deal with content annotation and commenting.