An ideal text for researchers and professionals alike, this book constitutes the refereed proceedings of the 5th International Symposium on Foundations of Information and Knowledge Systems, FoIKS 2008 held in Pisa, Italy, in February 2008. The 13 revised full papers are presented together with nine revised short papers and three invited lectures. All of these were carefully selected during two rounds of reviewing and improvement from a total of 79 submissions.