Descriptive models pretend to give a representation of the reality of any system that allows to study its real operation in an easy and flexible way to finally propose solutions and possible scenarios. The contributions of this paper include the following: 1. The design of a case study of a descriptive modeling for order supply chains; 2. An analysis of supply chains according to graph theory; 3. A simulation of one small business practical case to validate the model. Findings are related with using a case study with graph theory to analyze supply chain models in classroom in order to teach to the students the application in the companies of the theories seen in class.