This research proposes a new correctness notion, "group consistency", to relax the requirements of the global serializability among mobile transactions while data consistency can still be achieved. The basic idea is that read-only transactions (ROTs), being related by the requirements of application domains, are grouped together. ROTs in the same group together with update transactions are required to serialize with each other while ROTs in different groups are allowed to serialize with update transactions in different serialization orders. Under group consistency, two variants called group conflict consistency and group view consistency will be proposed. Interestingly, group consistency can be a generalization of a spectrum of different existing correctness criteria. With these relaxed consistency notions, transaction processing systems in mobile environments can be enhanced with a number of advantageous features consisting of autonomous processing of ROTs at mobile clients and increased concurrency due to reduced interference between groups of ROTs.