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Chapter 7. MDSD and SysML 167
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.
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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
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These 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.