This book studies data and knowledge transactions in mobile environments. A range of classical notions and protocols of transaction processing are rechecked and redefined in mobile environments. A relaxed serializability and a concurrency control method for mobile transactions are investigated. In addition to data transaction, knowledge transaction is explored in mobile environments. This book presents a knowledge transaction language and a model for use in mobile computing environments, and formalizes a framework/model that can be used to study knowledge transaction in mobile logic programming multi-agent systems. The formalized knowledge transaction language, model and framework are for knowledge transaction representation, formalization and knowledge reasoning in mobile environments.