The control-flow of business workflows is characterized by the strict execution order of the activities that is already defined at design time. This well-structured control-flow is for instance absolutely necessary if the workflows have to be performed fully automatically. However, this rigidity is not always appropriate for people-oriented workflows. Especially in scenarios where real world processes are only semi-structured humans should have more freedom to decide in which order they want to perform the activities. In this paper, we suggest an approach to design people-oriented workflows via constraints to make them more flexible.