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Assessing Requirements Quality through Requirements Coverage

Assessing Requirements Quality through Requirements Coverage. Ajitha Rajan University of Minnesota Mats Heimdahl University of Minnesota Kurt Woodham L3 Communications. Properties. Analysis. Testing. Prototyping. Visualization. Code. Model-Based Development. Specification Model.

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Assessing Requirements Quality through Requirements Coverage

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  1. Assessing Requirements Quality through Requirements Coverage Ajitha Rajan University of Minnesota Mats Heimdahl University of Minnesota Kurt Woodham L3 Communications

  2. Properties Analysis Testing Prototyping Visualization Code Model-Based Development Specification Model

  3. Model Validation problem • Are the requirements sufficiently defined for the system? • How well does the model implement the behaviors specified by the requirements? We propose a testing approach that explores the relationship betweenrequirements-based structural coverageandmodel-based structural coverage

  4. Are the Requirements Sufficient? Generate to provide requirements coverage Informal Requirements Run tests on the model and measure coverage achieved Measure Requirements-Based Tests Model / Design Specification (MUT) • Poor coverage of model implies one or more of the following • Missing or implicit requirements • Behavior in the model not derived from requirements • Requirements-based tests are inadequate

  5. Model Implements Requirements? Generate to provide model coverage Model/Design Specification Run tests on the requirements and measure coverage achieved Measure Model-Based Tests Requirements • Poor coverage of requirements implies one or both of the following • Model does not adequately implement behaviors specified in the requirements • Model is correct and requirements are poorly written

  6. Experimental Setup • Requirements Coverage Metric – Unique First Cause (UFC) coverage defined over formal LTL requirements • Model Coverage Metric – Modified Condition/Decision Coverage (MC/DC) • Four industrial case examples from the avionics domain • Two kinds of assessments • Generate test suites to provide requirements UFC coverage and measure MC/DC over the model • Generate test suites to provide MC/DC over the model and measure UFC achieved over formal requirements.

  7. Experiment Results MC/DC Achieved by Requirements-Based Tests

  8. Experiment Results • UFC metric “cheated” by the structure of requirements LTLSPEC G( var_a > ( case foo : 0 ; bar: 1 ; esac + case baz : 2 ; bpr : 3 ; esac )); LTLSPEC G( var_a > ( case foo & baz : 0 + 2 ; foo & bpr : 0 + 3 ; bar & baz : 1 + 2 ; bar & bpr : 1 + 3 ; esac ));

  9. Experiment Results Requirements UFC Coverage Achieved by Model-Based Tests

  10. Conclusions • Analyzing requirements coverage Vs model coverage provides a promising means of assessing requirements quality. • Effectiveness is dependent on the rigor and robustness of the coverage metrics used • UFC sensitive to the structure of the requirements

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