Abstract：The activities are closely related with time in workflow systems．How to guarantee that the activity is executed at a appropriate time has became the crucial problem in workflow systems．In this paper， temporal logic was used to solve this problem．Firstly，the concept of validity in workflow system was presented．Then propose a model of validity constraint based on temporal logic and the method to verify the validity constraint of the model．Finally，a instance is used for showing the validity of the method．
2010, Vol. 1 