Social networking forms an important part of online activities of Web users. Web sites such as Facebook, MySpace and Orkut
have millions of users using them everyday. However, these sites present two problems. Firstly, these sites form information silos.
Information on one site is not usable in the others. Secondly such sites do not allow users much control over how their personal
information is disseminated, which results in potential privacy problems.
In terms of decentralization, we have a framework as shown above, in which we have a user trusted server, where he /she can hold data (photos) without giving it to other social networking sites. The activities of a user (called news feed in Facebook) may be automatically updated when someone has tagged the user in a photo. In a decentralized setting, a user can be given more control of the news to be included in the feed.
Suppose User A wants to tag User B in a photo which is uploaded to User A’s trusted server. Since User A owns the photo, he can maintain any tag on his trusted server. The framework makes sure that User B will be notified when User A tags User B by sending a SPARQL update to Server B. User B can configure the settings on the server software which will accept or ignore the notification updates. It is up to User B to maintain knowledge of the existence of the photo uploaded by User A on his trusted server. User B can choose to generate corresponding news feed for this tagging event.