This book constitutes the thoroughly refereed post-workshop proceedings of the 8th International Workshop on Foundations of Models and Languages for Data and Objects, held in Dagstuhl Castle, Germany in September 1999. Seven long papers and three short papers are presented in revised full version. Also included is an invited paper by Veijalainen on Transactions in Mobile Electronic Commerce as well as two working group papers. The book presents recent results on all current aspects of database transactions processing, with an emphasis on electronic commerce applications.