  Merging operators aim at defining the beliefs/goals of a group of agents from
the beliefs/goals of each member of the group. Whenever an agent of the group
has preferences over the possible results of the merging process (i.e., the
possible merged bases), she can try to rig the merging process by lying on her
true beliefs/goals if this leads to better merged base according to her point
of view. Obviously, strategy-proof operators are highly desirable in order to
guarantee equity among agents even when some of them are not sincere. In this
paper, we draw the strategy-proof landscape for many merging operators from the
literature, including model-based ones and formula-based ones. Both the general
case and several restrictions on the merging process are considered.
