Quasi-star-cutsets and some consequences

This paper introduces a structural property of minimal imperfect graphs, no minimal imperfect graph has a quasi-star-cutset, before describing some consequences. First, a large class of perfect graphs is obtained from the class of all bipartite graphs and their line-graphs; this class contains several well-known classes of perfect graphs. The second consequence deals with a composition operation of graphs which preserves perfection and which encompasses the most part of the compositions known to preserve perfection.