Programming Languages and Systems

This volume contains the proceedings of the 4th Asian Symposium on Progr- mingLanguagesandSystems(APLAS2006),whichtookplaceinSydney,Japan, November 8-10, 2006. The symposium was sponsored by the Asian Association for Foundation of Software. In response to the call for papers, 70 full submissions were received. Each submission was reviewed by at least three Program Committee members with the help o...