Under this assumption, this corpus would be characterized as extremely incoherent, a claim belied both by native-speaker intuitions (an acceptable level of coherency for these texts was confirmed by three native speakers) and also by the fact that the task that was the central concern of these messages was successfully completed; the group exchanged a number of opinions and pieces of information and came to a consensus regarding their sports outing, with no message showing confusion about information contained in previous messages.
the solution of allowing only explicit centers does not yield an accurate characterization of the coherence of this corpus.