Processes support a powerful approach to the development of large-scale distributed applications spanning multiple, originally independent and heterogeneous stand-alone component systems. To this end, processes comprise services provided by these systems and integrate them into a coherent whole. Yet, a key factor for the success of this paradigm is the possibility to provide dedicated transactional execution guarantees. This book develops correctness criteria for the execution of transactional processes, thereby generalizing the traditional notions of concurrency control and recovery that can be found in databases and bringing them at a higher level of semantics. These criteria are supported by dynamic scheduling protocols which are based on a cost model for individual services. The benefit of this cost model is that it considerably supports the optimization of single process executions as well as the decision on how parallel processes can be interleaved. Finally, transactional coordination agents are introduced to address problems like heterogeneity and autonomy of component systems and to enhance services of these components by adding key transactional functionality. The combination of all these aspects forms the basis of a powerful and comprehensive framework for implementing middleware support for transactional process management.