The International Symposium on Abstraction, Reformulation and Approximation (SARA) series was established in 1994. It continues to provide a way for researchers to share results on ARA. The Ninth International Symposium on Abstraction, Reformulation and Approximation was held on July 17-18, 2011 at a renovated medieval castle in the Parador de Cardona hotel in Catalonia, Spain, about 60 miles northwest of Barcelona. This year the paper submissions came from four different continents and thirteen different countries. This volume contains all twenty of the papers that were accepted by the program committee for presentation at the symposium and publication in the proceedings.

The considerable interest in ARA techniques and the great diversity of the researchers involved had led to work on ARA being presented at many different venues. Consequently, there was a need to have a single forum where researchers of different backgrounds and disciplines could discuss their work on ARA. As a result, the Symposium on Abstraction, Reformulation, and Approximation (SARA) was established in 1994 after a series of workshops in 1988, 1990, and 1992. The current SARA, held at Lake Arrowhead, California, USA, on July 7-10, 2009, is the eighth in this series, following symposia in 1994, 1995, 1998, 2000, 2002, 2005, and 2007. Following a SARA tradition, this symposium brought together researchers with different backgrounds and facilitated lively discussions during and after the talks. There were 30 researchers from North and South America, Europe, and Australia. Additionally, SARA attendees were able to mingle and have fruitful discussions with members of the collocated Symposium on Combinatorial Search (SoCS). The collocation of SoCS was particularly useful in that many modern techniques in combinatorial search frequently utilize ARA methods. Finally, in addition to the regular and poster talks, there were three invited talks delivered by Jeff Orkin (Massachusetts Institute of Technology), Michael Genesereth (Stanford University), and Robert Holte (University of Alberta).