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To ensure global serializability, traditional distributed database systems implement both concurrency control and transaction commit protocols. In a distributed database systems, a commit protocol guarantees the uniform commitment of distributed transaction execution. In the last decade, several extensions to the transaction model adopted in traditional database systems have been proposed in order to support the functional and performance requirements of emerging advanced applications such as CAD/CAM, large software design projects and object-oriented databases. Nested transaction models have been shown to play an important role in such applications, however, these models are not yet fully studied. In this paper, our contributions in the field of real-time nested transactions are two fold: (i) we propose a hierarchical and flat protocols for real-time nested transactions, called 2PC-RT-NT, and (ii) we implement a lock mechanism, called 2LP-NT-HP, to solve the data conflicts problem between nested transactions.

Maintaining data temporal consistency in a Wire less Sensor Network (WSN) has attracted the attention of many researchers. Nowadays, there are many applications based on WSN which require consistent and valid measures to reflect the current state of the environment being monitored, or to quickly respond to some critical situations. In this paper, we propose a new query processing mechanism, giving each node the possibility to control the temporal validity of data in order to reduce the amount of invalid data delivered by WSN. We also provide a new query model, by introducing new SQL clauses, that allows the user setting the data validity interval and assigning a deadline to each query. Finally, we discuss the performances of our query processing approach and its capacity to maintain the data temporal consistency through two scenarios. The first scenario consists of injecting a single query in the network, then receiving periodic responses from sensors, during a period set by the user. In the second scenario, the user sends periodic queries to sensors according to an epoch, thereafter, it waits for query responses. We concluded by discussing the ability of network to maintain the data temporal consistency, based on the average of query responses time and the amount of valid data transmitted across the network.