  We present an algorithm for detecting service provider alliances. To perform
this, we modelize a cooperative game-theoretic model for competitor service
providers. A choreography (a peer-to-peer service composition model) needs a
set of services to fulfill its requirements. Users must choose, for each
requirement, which service providers will be used to enact the choreography at
lowest cost. Due to the lack of centralization, vendors can form alliances to
control the market. We propose a novel algorithm capable of detecting alliances
among service providers, based on our findings showing that this game has an
empty core, but a non-empty bargaining set.
