For example, when our customer here said he owns ???cars, which are
amortized over 6 years, using the ACRS algorithm,??? he is coupling cars to
a 6-year term and a particular algorithm for the write-off.
Commonality-Variability Analysis 163
Business people think of trends when they make decisions, which is
probably the right thing to do in business. As software professionals, we
have to look at these same issues differently; we want to look for opportunities
to decouple, encapsulate, and promote open-closed-ness for the
future value of the system. Business people certainly understand the value
of Return on Investment (ROI), but it is up to us to maximize it in the way
we model their business in software.
The result of considering these requirements purely in terms of what
is common and how those commonalities vary might produce the following
view. Commonalities will be shown in bold, underlined text, and
the variations within each common context will be listed in bullet points
below them.
164 Chapter 9 ??? Paying Attention to Practices
Assets
??? Real property
??? Automobiles
??? Office automation equipment
??? Furniture and fixtures
Amortization
??? Double-Declining
??? Straight Line
??? ACRS
??? Alternative Minimum Tax
Agencies
??? State
??? Federal Government
Commonality-Variability Analysis 165
Disposal Rules
??? Write off remaining value
??? Write off appraised value
??? Lose remaining value
Value Limits
??? Luxury car limit
Terms
??? 5 years
??? 33 years
??? 6 years
??? 3 years
Notes
There is only one Value Limit in the system right now, the one for
luxury cars.
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