Machine Learning and AI Applications in Astrophysics and Cosmology A workshop associated with the IJCAI-09 conference, http://ijcai-09.org/ Workshop co-organizers: Prof. S. George Djorgovski, Caltech, george*astro.caltech.edu Prof. Alexander Gray, Georgia Tech, agray*cc.gatech.edu Prof. Alex Szalay, JHU, szalay*jhu.edu [*=@] Astronomy has become an enormously data-rich science, with digital sky surveys detecting literally billions of sources across a full range of the electromagnetic spectrum, and measuring hundreds attributes for each. Such surveys and other data sets are now being federated within the Virtual Observatory framework. An effective data exploration and knowledge discovery from such highly complex and massive sets poses significant challenges, and calls for a more extensive use of AI/ML techniques, which should become a standard part of a scientist's toolkit. At the same time, interesting, challenging, but doable problems originating from the astrophysics and cosmology could help drive progress in the AI/ML field, and lead to broader advances. There is a great synergistic opportunity here, for both of these communities. This workshop will bring together the pioneering or established practitioners of the use of ML/AI tools and methodologies in astronomy and cosmology, as well as some newcomers to the field. We will review briefly the past accomplishments and current practices and challenges, but the main focus would be on defining the new paths for future exploration and collaboration, including some specific problems and challenges which could be tackled over the next few years. We will aim for a roughly equal balance between computing-savvy astrophysicists and applied computer scientists. Our goal is to foster stronger connections between the AI/ML community and the data intensive astronomy / virtual observatory community. We will aim for a roughly equal balance between astronomers and computer scientists, an for a total number of about 30 to 40 participants, small enough for some real discussions, and yet achieving a critical mass. We aim to inform better both of these communities about each other's interests and challenges, and to facilitate and foster new interdisciplinary collaborations between them. This meeting will also serve as a forum to evaluate critically the past successes and failures, and derive some constructive lessons from them. Finally, we expect that the participants would go on to become even more effective community evangelists for the use of AI/ML methods in data-intensive astronomy and cosmology. The workshop would last 2 days, and would be heavily biased towards discussions, both structured/moderated and informal (during the breaks). We will invite a number of keynote or review talks, with explicit instructions to the speakers to focus on the challenges and prospects for the future, and to be constructively provocative, rather than to simply describe their recent results. There would be no contributed talks, but we would allow for posters.