  We consider the problem of exact synchronization of two rankings at remote
locations connected by a two-way channel. Such synchronization problems arise
when items in the data are distinguishable, as is the case for playlists,
tasklists, crowdvotes and recommender systems rankings. Our model accounts for
different constraints on the communication throughput of the forward and
feedback links, resulting in different anchoring, syndrome and checksum
computation strategies. Information editing is assumed of the form of
deletions, insertions, block deletions/insertions, translocations and
transpositions. The protocols developed under the given model are order-optimal
with respect to genie aided lower bounds.
