IBM SG24-7368-00 manual Model Driven Systems Development with Rational Products

Figure 7-17 Diagram with restaurant with constraint equation: Profit = Revenue – Costs

We can see from both the equations and the diagram that the number of meals served plays a significant role in the profitability of the restaurant. We want to do further analysis and simulation on how we might increase the number of meals served. We will, however, be constrained by factors such as the size of the restaurant—after a certain point, increasing profit might mean creating new restaurants; you can only constrain salaries by so much; you can only charge what market in your area will bear, if you decrease the quality of your ingredients to reduce meal costs, you risk losing customers, and so on. We can express these in further equations and diagrams, associate data with them, and since the model now is populated with data, we will be able to hook it to a simulation engine.

Let us take another example. If we are building a radar, we will most likely need to consider its range as a requirement as well as its size and weight

(Figure 7-18).

168Model Driven Systems Development with Rational Products