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Chapter 13 - Modeling Text-Based Require... > 13.2 Requirement Diagram - Pg. 318

318 CHAPTER 13 Modeling Text-Based Requirements specifications are typically organized in the model into a hierarchical package structure that corre- sponds to a specification tree. Each specification contains multiple requirements, such as a systems specification that contains the requirements for the system, or the component specifications that contain the requirements for each component. The requirements contained in each specification are often modeled in a tree structure that corresponds to how each specification is organized. The indi- vidual or aggregate requirements within the containment hierarchy can then be linked to other requirements in other specifications, and to model elements that represent the system design, analysis, implementation, and test cases. SysML includes requirements relationships for derivation, satisfaction, verification, refinement, and trace that support a robust capability for relating requirements to one another and to other model elements. In addition to capturing the requirements and their relationships, SysML includes a capa- bility to capture the rationale, or basis for a particular decision, and for linking the rationale to any model element. This includes linking the rationale to a requirement or to a relationship between the requirement and other model elements. A copy relationship is also provided to accommodate appropriate reuse of requirement text. Each individual text requirement can be captured in the model as a SysML requirement. The requirement construct includes a name, text string, and id, and may also include additional user defined properties such as risk.