IBM SG24-7368-00 manual Parametrics

Parametrics

Perhaps the most important addition of SysML is the capability it gives us to reason about systems concerns through parametrics, and through its more accurate semantics regarding non-functional and other concerns. This topic needs a book in its own right; we will limit ourselves here to a few illustrative examples that will hopefully demonstrate its power.13

Let us look at two examples: restaurant profitability, and radar range.

In “Restaurant ownership” on page 7 we used a restaurant as an example of some of the issues you can reason about with MDSD. Let us take a simplified profitability equation, and diagram it in SysML.

Clearly, profit is generally the difference between revenue and expenses (of all types, including taxes). Let us assume the revenue from the restaurant comes the price of the meals (for simplicity, we consider only meals and not drinks) times the number of meals. Costs are the cost of ingredients, salaries, and rent (or mortgage). See Figure 7-17.

profit = revenue - expenses

revenue = number of meals * price of meal

expenses = ((number of meals)*cost of meal (ingredients)) + salaries + rent

rent = square footage * location factor

13These examples are drastically over-simplified for pedagogical purposes. For a more detailed discussion of parametrics with examples, see RS Peak, RM Burkhart, SA Friedenthal, MW Wilson, M Bajaj, I Kim (2007) Simulation-Based Design Using SysML—Part 1: A Parametrics Primer. International Council on Systems Engineering (INCOSE) Intl. Symposium, San Diego, and RS Peak, RM Burkhart, SA Friedenthal, MW Wilson, M Bajaj, I Kim (2007) Simulation-Based Design Using SysML—Part 2: Celebrating Diversity by Example. INCOSE Intl. Symposium, San Diego.

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