ABAP_to_the_Future

Any fool can make a rule
And any fool will mind it.
—Henry David Thoreau, Journal #14
9 BRFplus
It is one of the great truths in life that rules are with us always—just like death
and taxes—and the same is true in SAP. A business rule defines what outcomes
should occur based upon the values of one or more input criteria. An example is
as follows: “Australians wh o do not have private health care have to pay 2.5%
extra income tax.” In this case, the input criterion is whether any given individual
has such insurance; the outcome is whether or not that individual has to pay more
tax.
A business rules framework (BRF), also known as a business rule management system
(BRMS), is a framework that enables you to express such rules within your
computer system. It consists of three components: a UI, a rules repository, and a
rules engine. An example of a business rules framework—and the subject of this
chapter—is, of course, BRFplus.
One of the purposes of a business rules framework is to isolate a process from the
decision logic that is a part of that process. A process is the high-level end goal
achieved by a set of decisions—for example, the process of making monsters. Processes
tend to be the same for all companies and very rarely change; in OO programming
terms, the process is the abstraction, which cares not about the details.
The decision logic, on the other hand, is the indivi dual decisions that go into the
bigger process. This can be very di fferent between companies and can also
change all the time. No two mad scientists can agree on what the best recipe is for
making a monster or which is the best so rt of hunchback to assist them. In OO
programming terms, these are the details, which depend upon the abstraction.
In Figure 9.1, you can see the differen ce between a process and the decisions in
that process.
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