This book constitutes the thoroughly referred post-proceedings of the 11th Conference of the Spanish Association for Artificial Intelligence, CAEPIA 2005, held in Santiago de Compostela, Spain in November 2005.

The 48 revised full papers presented together with an invited paper were carefully selected during two rounds of reviewing and improvement from an initial total of 147 submissions. The papers span the entire spectrum of artificial intelligence from foundational and theoretical issues to advanced applications in various fields.

The idea of soft computing emerged in the early 1990s from the fuzzy systems c- munity, and refers to an understanding that the uncertainty, imprecision and ig- rance present in a problem should be explicitly represented and possibly even - ploited rather than either eliminated or ignored in computations. For instance, Zadeh de?ned 'Soft Computing' as follows: Soft computing differs from conventional (hard) computing in that, unlike hard computing, it is tolerant of imprecision, uncertainty and partial truth. In effect, the role model for soft computing is the human mind. Recently soft computing has, to some extent, become synonymous with a hybrid approach combining AI techniques including fuzzy systems, neural networks, and biologically inspired methods such as genetic algorithms. Here, however, we adopt a more straightforward de?nition consistent with the original concept. Hence, soft methods are understood as those uncertainty formalisms not part of mainstream s- tistics and probability theory which have typically been developed within the AI and decisionanalysiscommunity.Thesearemathematicallysounduncertaintymodelling methodologies which are complementary to conventional statistics and probability theory.