This book constitutes the refereed proceedings of the 12th International Workshop on Cooperative Information Agents, CIA 2008, held in Prague, Czech Republik, in September 2008.

Invited Contributions.- Enabling Networked Knowledge.- Coordination and Agreement in Multi-Agent Systems.- Agents and Databases: A Symbiosis?.- Agents and Semantic Services: A Critical Review.- Agent-Supported Planning in Distributed Command and Control Environments.- Trust.- Towards Trust-Based Acquisition of Unverifiable Information.- Modeling Dynamics of Relative Trust of Competitive Information Agents.- A Formal Approach to Aggregated Belief Formation.- Applications.- Software Engineering for Service-Oriented MAS.- A Service-Oriented MultiAgent Architecture for Cognitive Surveillance.- Trust-Based Classifier Combination for Network Anomaly Detection.- A Distributed Generative CSP Framework for Multi-site Product Configuration.- MobiSoft: Networked Personal Assistants for Mobile Users in Everyday Life.- A Web-Based Virtual Machine for Developing Computational Societies.- Using the Wizard of Oz Method to Train Persuasive Agents.- ASBO: Argumentation System Based on Ontologies.- Coordination and Communication.- Controling Contract Net Protocol by Local Observation for Large-Scale Multi-Agent Systems.- Filter Allocation Using Iterative ECNP.- On the Use of Symbolic Data Analysis to Model Communication Environments.- Commitment-Based Multiagent Decision Making.- Negotiation.- Towards an Open Negotiation Architecture for Heterogeneous Agents.- Incrementally Refined Acquaintance Model for Consortia Composition.- Towards a Monitoring Framework for Agent-Based Contract Systems.- Collaborative Load-Balancing in Storage Networks Using Agent Negotiation.