**3.6. Verification**

When the model is built up, it should be verified to see whether it reflects the system operation as defined with data about the production process. Some interesting properties of the model can be checked with the P-invariant analysis. Several P-invariants can be identified in the model. Their number is defined with the sum of all the resources, the number of product routes and the number of all precedences that are present in the model. It can be stated that the weighted sum of tokens that belongs to every P-invariant, which is a consequence of a resource, is equal to the capacity of that resource. The weighted sum of all other invariants is defined with the common number of batches of demanded product.

If possible, the model is later simplified in a way, that eliminated nodes do not influence the model behaviour.
