As we know, software development process includes
requirement analysis, design, coding and testing etc. These
steps are defined as the transition, condition, or status of
process or a resource are defined as the place, and resources
like staff, software or hardware are defined as tokens in the
Petri nets model. Fig. 4 shows Petri nets modeling for
development process step in a software project. i P and j R
which are places, represent the status of the project and
resources. The real number in place i P represents the
amount of tasks. The tokens represented by dots indicate the
resources. The transition i T corresponds to the step of
software development process. The token in 1 R are different
from those in 2 R because the resources in each step are not
the same. According to the firing rule of a Petri net,
transitions are enabled for execution when tokens satisfy the
firing condition. That is to say the corresponding step will
be transformed to other step when the conditions and
resources are satisfied.