This is a subject that is as hot as a snake in a wagon rut, offering as it does huge potentiality in the field of computer programming. That's why this book, which constitutes the refereed proceedings of the 7th International Symposium on Abstraction, Reformulation, and Approximation, held in Whistler, Canada, in July 2007, will undoubtedly prove so popular among researchers and professionals in relevant fields. 26 revised full papers are presented, together with the abstracts of 3 invited papers and 13 research summaries.