Guiding Scenario Authoring

Since a few years, scenario based requirements engineering approaches have gained in popularity. Textual scenarios are narrative descriptions of flows of actions between agents. They are often proposed to elicit, validate or document requirements. The CREWS experience has shown that the advantage of scenarios is their easiness of use, and that their disadvantage stands in the lack of guidelines for authoring. In this article, we propose guidance for the authoring of scenarios. The guided scenario authoring process is divided into two main stages : the writing of scenarios, and the correcting of scenarios. To guide the writing of scenarios, we provide style and contents guidelines referring to a conceptual and a linguistic model of scenarios. To guide the correcting of scenarios, we propose a set of enactable rules. These rules aim at the clarification, completion and conceptualisation of scenarios, and help the scenario author to improve his scenarios until acceptable quality in the terms of the former scenario models. The paper presents both style / contents guidelines, and correction rules, and illustrates them with the London Ambulance Service example.