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<mainDescription>&lt;h3>&#xD;
Definition&#xD;
&lt;/h3>&#xD;
&lt;p>&#xD;
System-wide requirements are requirements that&amp;nbsp;define necessary system quality attributes&amp;nbsp;such as&#xD;
performance, usability and reliability, as well as global functional requirements&amp;nbsp;that are not captured in&#xD;
behavioral requirements artifacts such as use cases.&#xD;
&lt;/p>&#xD;
&lt;h3>&#xD;
System-wide&amp;nbsp;Requirements Categories&#xD;
&lt;/h3>&#xD;
&lt;p>&#xD;
System-wide&amp;nbsp;requirements are categorized according to the FURPS+ model (Functional, Usability, Reliability,&#xD;
Performance, Supportability + constraints). Constraints&amp;nbsp;include design, implementation, interfaces, physical&#xD;
constraints, and business rules. A description of each of these types of requirements follows.&#xD;
&lt;/p>&#xD;
&lt;p>&#xD;
System-wide requirements and use cases, together, define the requirements of the system. These requirements support the&#xD;
features listed in the vision statement. Each requirement should&amp;nbsp;support at least one feature, and each feature&#xD;
should be supported by at least one requirement.&#xD;
&lt;/p>&#xD;
&lt;p>&#xD;
In general, &lt;strong>functional&lt;/strong> requirements describe behavior and can be captured as&amp;nbsp;use cases.&#xD;
&lt;strong>Non-functional&lt;/strong> requirements are captured in a system-wide requirements specification.&amp;nbsp;However,&#xD;
nonfunctional requirements that are closely associated with a particular use case are often captured within the&#xD;
use-case specification itself to simplify communication and maintenance.&amp;nbsp;Similarly, there are global, or&#xD;
system-wide functional requirements that are often captured among the system-wide requirements for the same&#xD;
reasons.&amp;nbsp;&#xD;
&lt;/p>&#xD;
&lt;h4>&#xD;
Functional requirements&#xD;
&lt;/h4>&#xD;
&lt;p>&#xD;
Functional requirements include all the over-arching, system-wide functional requirements that are not expressed as use&#xD;
cases. These functional requirements represent the main system features that are familiar within the business domain or&#xD;
technically oriented requirements such as auditing, licensing, localization, e-mail, online help, printing, reporting,&#xD;
security, system management, or workflow.&#xD;
&lt;/p>&#xD;
&lt;h4>&#xD;
Usability requirements&#xD;
&lt;/h4>&#xD;
&lt;p>&#xD;
Usability requirements include requirements based on human factors and user-interface issues such as accessibility,&#xD;
interface aesthetics, and consistency within the user interface.&#xD;
&lt;/p>&#xD;
&lt;h4>&#xD;
Reliability requirements&#xD;
&lt;/h4>&#xD;
&lt;p>&#xD;
Reliability requirements include aspects such as availability, accuracy, predictability, frequency of failure or&#xD;
recoverability of the system from shut-down failure.&#xD;
&lt;/p>&#xD;
&lt;h4>&#xD;
Performance requirements&#xD;
&lt;/h4>&#xD;
&lt;p>&#xD;
Performance requirements address concerns such as throughput of information through the system, system response time&#xD;
and resource usage.&#xD;
&lt;/p>&#xD;
&lt;h4>&#xD;
Supportability requirements&#xD;
&lt;/h4>&#xD;
&lt;p>&#xD;
Supportability requirements include&amp;nbsp;requirements such as compatibility and the abilities to test, adapt, maintain,&#xD;
configure, install, scale, and localize the system.&#xD;
&lt;/p>&#xD;
&lt;h4>&#xD;
+ Constraints&#xD;
&lt;/h4>&#xD;
&lt;p>&#xD;
The &lt;strong>+&lt;/strong> of the FURPS+ acronym allows you to specify constraints, such as design, implementation,&#xD;
interfaces, physical constraints, and business rules:&#xD;
&lt;/p>&#xD;
&lt;ul>&#xD;
&lt;li>&#xD;
&lt;strong>Design constraints&lt;/strong> limit the design and state requirements on the approach that should be taken in&#xD;
developing the system.&#xD;
&lt;/li>&#xD;
&lt;li>&#xD;
&lt;strong>Implementation constraints&lt;/strong> put limits on coding or construction (required standards, languages,&#xD;
tools, or platform)&#xD;
&lt;/li>&#xD;
&lt;li>&#xD;
&lt;strong>Interface constraints&lt;/strong> are requirements to interact with external systems, describing protocols or&#xD;
the nature of the information that is passed across that interface.&#xD;
&lt;/li>&#xD;
&lt;li>&#xD;
&lt;strong>Physical constraints&lt;/strong> affect the hardware or packaging housing the system (shape, size, and&#xD;
weight).&#xD;
&lt;/li>&#xD;
&lt;li>&#xD;
&lt;strong>Business rules&lt;/strong> are policies or decisions that govern how the business operates. They may constrain&#xD;
the steps described in the us-case flow.&#xD;
&lt;/li>&#xD;
&lt;/ul></mainDescription>
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