A Study of Central Auction Based Wholesale Electricity Markets -- The Choice of Eliminating the Uncertainty Cloud in Auctions -- Eliciting Expert Advice in Service-Oriented Computing -- Approximating the Qualitative Vickrey Auction by a Negotiation Protocol -- Automated Analysis of Auction Traces -- Mechanism Design for the Online Allocation of Items without Monetary Payments -- A Demand-Driven Approach for a Multi-Agent System in Supply Chain Management -- Mechanism Design for Eliciting Probabilistic Estimates from Multiple Suppliers with Unknown Costs and Limited Precision -- Nash Social Welfare in Multiagent Resource Allocation -- Leading a Best-Response Teammate in an Ad Hoc Team -- Designing an Ad Auctions Game for the Trading Agent Competition -- Robust Planning and Control Using Intelligent Products -- How Specialised Are Specialists? Generalisation Properties of Entries from the 2008 and 2009 TAC Market Design Competitions -- Learning Improved Entertainment Trading Strategies for the TAC Travel Game -- Evaluation of Market Design Agents: The Mertacor Perspective -- Continuous Double Auctions with Execution Uncertainty -- Sequential Auctions with Partially Substitutable Goods -- From General Game Descriptions to a Market Specification Language for General Trading Agents.

This volume contains 18 thoroughly refereed and revised papers detailing recent advances in research on designing trading agents and mechanisms for agent-mediated e-commerce. They were originally presented at the 11th International Workshop on Agent-Mediated Electronic Commerce (AMEC 2009) collocated with AAMAS 2009 in Budapest, Hungary, or the 2009 Workshop on Trading Agent Design and Analysis (TADA 2009) collocated with IJCAI 2009 in Pasadena, CA, USA. The papers focus on topics such as individual agent behavior and agent interaction, collective behavior, mechanism design, and computational aspects, all in the context of e-commerce applications like trading, auctions, or negotiations. They combine approaches from different fields of mathematics, computer science, and economics such as artificial intelligence, distributed systems, operations research, and game theory.