The central behavioral element is a work package. A work package is a behavior element that has a clearly defined start and end date, and realizes a well-defined set of goals or deliverables. The work package element can be used to model sub-projects or tasks within a project, complete projects, programs, or project portfolios.
Conceptually, a work package is similar to a business process, in that it consists of a set of causally-related tasks, aimed at producing a well-defined result. However, a work package is a unique, “one-off” process. Still, a work package can be described in a way very similar to the description of a process.