Binary approach of affinity propagation

Question

I'm implementing the Binary Variable Model for Affinity Propagation and have a conceptual doubt about it.

I can understand most of the algorithm and have my implementation working, but I don't understand why is not needed to send both values for the messages and why after adding incoming messages positive values correspond to one and negative to zero.

Thanks

Answer 1

An explanation can be found at Frey and Dueck 2007