We are pleased to present the proceedings of the 12th International Conference on Discovery
Science (DS 2009) held in Porto Portugal October 3 5 2009. DS 2009 was collocated with ALT
2009 the 20th International Conference on AlgorithmicLearningTheory
continuingthesuccessfulDSconferenceseries. DS 2009 provided an open forum for intensive
discussions and the exchange of new ideas among researchers working in the area of discovery
science. The scope of the conference included the development and analysis of methods for
automatic scienti?c knowledge discovery machine learning intelligent data analysis and
theory of learning as well as their applications. We were honored to have a very strong
program. Acceptance for the conference proceedings was very compe- tive. There were 92 papers
submitted with the authors coming from roughly 20 di?erent countries. All paperswere
reviewedby three senior researchersfollowed by an extensive discussion. The program committee
decided to accept 23 long papers (an acceptance rate of 25%) and 12 regular papers. The overall
acc- tance rate was 38%. The contributed papers cover a wide range of topics from discovery in
general to data mining in particular. In addition to the technicalpapers we weredelighted to
have?ve prestigious invited speakers and two tutorials. Fernando Pereira University of Penns-
vania USA presented new fundamental questions that should be investigated in natural language
processing in web mining. Hector Ge?ner from Pompeu Fabra University Spain discussed
learning methods for solving complete pl- ning domains.
