The disadvantage of the concept of temporal consistency is that it only describes binary states of real-time data objects. The concept of validity degree function is presented to overcome the problem. Based on the new concept

two sensor transaction scheduling schemes VM-DS and VM-SN are proposed. Both schemes maximize the data validity degree by judiciously setting the lengths of data validity intervals and the execution frequencies of sensor transactions. Experiments are conducted to evaluate the performance of two schemes. The results show VM-SN outperforms in terms of the average data validity degree and the ratio of validity degree to workload

thus it can better satisfy the timeliness requirements of the systems.