  Independent set games are cooperative games defined on graphs, where players
are edges and the value of a coalition is the maximum cardinality of
independent sets in the subgraph defined by the coalition. In this paper, we
investigate the convexity of independent set games, as convex games possess
many nice properties both economically and computationally. For independent set
games introduced by Deng et al. (Math. Oper. Res., 24:751-766, 1999), we
provide a necessary and sufficient characterization for the convexity, i.e.,
every non-pendant edge is incident to a pendant edge in the underlying graph.
Our characterization immediately yields a polynomial time algorithm for
recognizing convex instances of independent set games. Besides, we introduce a
new class of independent set games and provide an efficient characterization
for the convexity.
