Invited Papers -- Easy Yet Hard: Model Checking Strategies of Agents -- Programming Multi-agent Systems -- Regular Papers -- Verifying Agents' Conformance with Multiparty Protocols -- Run-Time Semantics of a Language for Programming Social Processes -- Embedding Linear-Time Temporal Logic into Infinitary Logic: Application to Cut-Elimination for Multi-agent Infinitary Epistemic Linear-Time Temporal Logic -- Bounded-Resource Reasoning as (Strong or Classical) Planning -- A Formal Framework for User Centric Control of Probabilistic Multi-agent Cyber-Physical Systems -- Revisiting Satisfiability and Model-Checking for CTLK with Synchrony and Perfect Recall -- Contracts Violation: Justification via Argumentation -- Argument-Based Decision Making and Negotiation in E-Business: Contracting a Land Lease for a Computer Assembly Plant.

This book constitutes the thoroughly refereed and revised proceedings of the 9th International Workshop on Computational Logic for Multi-Agent Systems, CLIMA IX, held in Dresden, Germany, in September 2008 and co-located with the 11th European Conference on Logics in Artificial Intelligence, JELIA 2008. The 8 full papers, presented together with two invited papers, were carefull selected from 18 submissions and passed through two rounds of reviewing and revision. Topics addressed in the regular papers include the use of automata-based techniques for verifying agents' conformance with protocols, and an approach based on the C+ action description language to provide formal specifications of social processes such as those used in business processes and social networks. Other topics include casting reasoning as planning and thus providing an analysis of reasoning with resource bounds, a discussion of the formal properties of Computational Tree Logic (CTL) extended with knowledge operators, and the use of argumentation in multi-agent negotiation. The invited contributions discuss complexity results for model-checking temporal and strategic properties of multi-agent systems, and the challenges in design and development of programming languages for multi-agent systems.