Figure 8 6 example of the three types of requirements

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Figure 8-6 Example of the three types of requirements traceability In addition, figure 8-6 shows the traceability between requirements. The traceability link between requirement “R-14” and “R-11” documents that requirement “R-14” was derived from requirement “R-11”. 8.4.4 Representation of Requirements Traceability Requirements traceability information can be represented in different ways. The most common approaches to representing traceability are sim- ple textual references, hyperlinks, and trace matrices and trace graphs. Stakeholder “We want to gain technological market leadership by 2010.” Company Strategy Document V.12 “The customer desires the simplest possible interaction with the navigation system”. R-14: The navigation system shall offer the user the ability to enter the destination via voice command. Rough design Refined design realized through R-11: The navigation system must be able to receive voice commands from the user. Implementation Pre-RS traceability Test cases is derived from Post-RS traceability Traceability between requirements
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126 8 Requirements Management Text-Based References and Hyperlinks This simple way to represent traceability information of a requirement consists of annotating the target artifact as a textual reference in the requirement (initial artifact) or to establish a hyperlink between the initial artifact and the target artifact. When linking artifacts, different types of hyperlinks with specific link semantics can be used. Trace Matrices Another common technique for representing and documenting traceabil- ity information between requirements as well as between requirements and previous and posterior artifacts in the development process are trace matrices. The rows in a trace matrix contain the initial artifacts (require- ments). In the columns, the target artifacts (e.g., sources of requirements, development artifacts, requirements) are represented. If a trace link exists between an initial artifact in row n and a target artifact in column m , cell (n, m) is marked in the trace matrix. Interpretation of a trace matrix Figure 8-7 shows a simple trace matrix for the trace relation “derived” that exists between two requirements. An entry in the matrix specifies that a trace link of type “derived” exists from a requirement “ Req-n ” to another requirement “ Req-m ” such that “ Req-n ” was derived from “ Req-m ”. Figure 8-7 Representation of traceability information in a trace matrix Maintainability of trace matrices In practice, it became apparent that trace matrices are difficult to maintain as the number of requirements increases. A trace matrix that, for example, documents the refinement relations between merely 2,000 requirements contains over four million cells. In addition, many trace matrices must be created in order to be able to represent the available information cleanly (e.g., with regard to different types of traceability links).
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