Perminder Sahota

Praxis Critical Systems, London, UK

THE USE of scenarios to elicit and validate requirements as complete, correct, and testable is becoming increasingly popular. One of the few tested methods available for systematic and interactive scenario generation and walkthrough is CREWS-SAVRE (Co-operative Requirements Engineering With Scenarios-Scenarios for Acquiring and Validating Requirements).

CREWS-SAVRE is a process with supporting software tools. It was developed as part of the EU-funded Framework IV crews long-research project to support the systematic and domain-independent generation and walking through of scenarios described in Chapter 9. Design of the software scenario walkthrough tool was based on a cognitive principle familiar from prototyping—that people recognise items, such as events, better than they recall them with from memory. Therefore, CREWS-SAVRE automatically generates and presents candidate exceptions that stakeholders recognise as relevant and possible, helping people to generate new requirements and so reducing the risk of missing requirements.

This case study reports on an experience within Eurocontrol that used the CREWS-SAVRE walkthrough approach to help specifying the requirements for a state-of-the-art air traffic control system. The project was called CORA-2 (COnflict Resolution Assistant).


The CREWS-SAVRE approach to scenario walkthroughs adopted for CORA-2 is part of the ...

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