On the and-or-scheduling problems

In the and-or scheduling model, a project consists of several tasks. Each task has a duration attribute. A task can be performed only when all of its requirements are satisfied. After a task is completed, more requirements become satisfied. A characteristic of the AOscheduling projects is that a requirement may be satisfied in several ways. Several questions concerning AOscheduling might be interesting, including whether the project can be completed, the earliest time a project can be completed, the minimal number of processors needed to complete the project, and assigning tasks to processors, etc. We use Petri nets and segment graphs to analyze AOscheduling projects.