Programming Languages and Systems : Springer : 9783540237242 : 3540237240 : 15 Oct 2004 : On behalf of the organizing committee I would like to welcome you all to the second Asian Symposium on Programming Languages and Systems (APLAS 2004) held in Taipei on November 4?6, 2004. Since the year 2000, researchers in the area of programming languages and systems have been meeting annually in Asia to present their most recent research results, thus contributing to the advancementofthisresearcharea.ThelastfourmeetingswereheldinSingapore (2000), Daejeon (2001), Shanghai (2002), and Beijing (2003). These meetings were very fruitful and provided an excellent venue for the exchange of research ideas, ?ndings and experiences in programming languages and systems. APLAS 2004 is the ?fth such meeting and the second one in symposium setting. The ?rst symposium was held in Beijing last year. The success of the APLAS series is the collective result of many people's contributions.ForAPLAS2004,?rstIwouldl