Representing relation between posts

Hi all,

is there a preferred way to represent the relation between posts in 
different Social Sites? For example, it is now pretty common to post to 
Twitter, and this post becomes a post in my wall in Facebook. It would 
be nice to represent the relation between these two posts.
I don't think this can be represented directly using SIOC, for instance.

Cheers
D

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Prof. Daniel Schwabe
Dep. de Informática, PUC-Rio
R. M. de S. Vicente, 225, Rio de Janeiro, RJ 22453-900
Tel. +55 21 3114 1500  x. 4356