A workflow management system is a software system to assist designing processes, controlling and managing the execution of the designed processes. One emerging trend in many recent information systems is the provision of process management functions. In this paper, we propose a method of designing processes for automatic process execution directly from process modeling. First of all, the concept of block is presented which is to define a nested process model. A block is the minimum unit that can specify the relationships of process components, i.e., tasks. A general process can be defined by a combination of the blocks defined in this paper. An algorithm is developed to transform a general flat process model into a nested model. We identify basic types of blocks and build ECA (Event-Condition-Action) rules for each of the basic types. This allows us to automate the execution of the process model by using the active features of active databases.