Building the Core – Enterprise Business Flows - Applied SOA Patterns on the Oracle Platform - page 216

sure you that we will rebuild it for better association with SOA Patterns and as a result
provide better performance, maintainability, and scalability. Anyway, you can be rest as-
sured that the presented solution is already solid enough and it works!
We could only have the Business Rule component in our EP lookup composite, but again,
we will add the Mediator. Why is that? For its transformation and routing support, of
course. Again, following the SOA principles, we want to maintain PlanLookupSer-
vice in an atomic state, decoupled from the MessageHeaders implementation. The
MH XSD can evolve, following our understanding of business requirements and the
SBDH standard; also, we definitely do not want to affect our Rule Facts, which are
already implanted into the decision service. Another important thing is the flexibility of
the Rule Engine itself. We can have more than one ruleset, supporting multiple decision
tables or rule functions. Thus, we should not only transform message headers' values from
an inbound request into rule function parameters (see the callFunctionStateless
transformation in the following screenshot, the Transform Using field), but also route in-
dividual requests to the specific decision table (or rule function). Static routing will do
perfectly fine here.
You can see how many operations we can support from the client's perspective with our
service in the previous screenshot from the previous paragraph; all operations are syn-
chronous, which is logical because async MEPs simply will not work here.
Talking about the Rule Centralization SOA pattern, we have to stress the fact that concen-
trating on all the rules in the form of heavy decision tables in one decision service is not a
good idea at all. The rule of the thumb here would be to centralize all the business deleg-
ates' decision tables in one decision service and separate it from other business domains
(see the corresponding BusinessDomain element in the following mapping):