A Business Model that includes Business Entities and Business Rules can be used to define services that encapsulate the business
rules. Figure 1 demonstrates a small, sample business-analysis model showing two business rules
attached to the business entity named Order. These rules, as they are attached to a business entity, are most likely to
correspond to invariants on the entity and so will be evaluated on any change in state of the entity. Rules also
can be attached to actions or processes. Such rules more often are evaluated as pre-conditions or
post-conditions for the action.
Figure 1. Business analysis model
In modeling the example above, it is assumed that there is a traceable relationship between the ServiceInterfaces derived from the business rules and between the message(s) derived from the business entity.
In many cases. complex rules are aggregated into Rule Sets. These are much more of a match for the granularity of a
service, allowing, for example, a document to be passed to the validation service where the set of rules are evaluated
and the results returned. From the example above, we can easily imagine that the validation services actually embody
quite a complex set of rules for validating the compatibility of items ordered, quantities, and so on.
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