  Although social networking has become a remarkable feature in the Web, full
interoperability has not arrived. This work explores the main 5 paradigms of
interoperability across social networking sites, corresponding to the layers in
which we an find interoperability. Building on those, a novel analytical
framework for SNS interoperability is introduced. Seven representative
interoperability SNS technologies are compared using the proposed framework.
The analysis exposes an overwhelming disparity and fragmentation in the
solutions for tackling the same problems. Although there are a few solutions
where consensus is reached and are widely adopted (e.g. in object IDs), there
are multiple central issues that are still far from being widely standarized
(e.g. in profile representation). In addition, several areas have been
identified where there is clear room for improvement, such as privacy controls
or data synchronization.
