Page 93 - Software and Systems Requirements Engineering in Practice

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C h a p t e r 3 : E E l i c i t i n g R e q u i r e m e n t s 63 63
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or product delivery. It is mandatory that the customer have the ability
to alter the rules without system or product modification.
Example Customer-Specific Business Rules
A sample business policy, rules, and some derived requirements are
shown here:
• Policy The hospital shall be able to define the difference
between adult and child patients for check-in and medical
records purposes.
• Rule Any patient under the age of 14 checking in shall be
considered a child.
When a child checks into the hospital, depending on the
hospital’s business policy, a parent or guardian may have to
accompany the child and sign all the admission forms.
Detailed rules explain under what circumstances (e.g., an
accident, emergency, or life-threatening situation) a child
may be checked in without a parent’s or guardian’s consent.
• Requirement A facility shall be provided with the system
such that the hospital check-in process for adults and children
can be changed by hospital administrators without the need
for system or software modifications.
Note in the preceding example, the hospital may, at any time,
change the age at which a patient is considered a child, as well as the
rules governing the emergency check-in of a child without parental
consent. The relationships among business policies, rules, and
requirements are illustrated in Figure 3.13.
Based on
Business Rule Basis for Policy
Statement
Related to Part of
composed of
Formal
Expression Type Source
of
Based
In the on Business
convention Requirement
of
An Source of Source of
expression
Formal Rule of Business
System
Statement Expressed Rule Source of Requirement
in
FIGURE 3.13 Business policies, rules, and derived requirements