In contrast to the top-down approach, the bottom-up approach starts with defining the activities that stand at the base of the process model. Using them, many different and detailed business processes are created, describing how low level business requirements are fulfilled. The goal of the model is to show how a specific activity is performed to produce a value at the end of the process. In other words, this approach focuses on the subprocesses first. This detailed view of them helps developers and system architects to make the process work. However, a problem occurs when this abundance of details has to be combined to form the overall model picture or when it comes to defining the key requirements the general model should fulfill.
In the process composer, you can use the bottom-up approach to model a process focusing on the details of the process steps. After defining the process steps details, that is to say the business logic of the steps, you can combine them to create the process model. With this approach, the process modeling includes the following steps:
Creating and importing the business logic of the process steps (tasks, Web services, rules).
Creating a process.
Creating the process steps, represented by activities (human, automated, subprocess).
The activities have tasks and Web services assigned to them.