Ahab´s Leg dilemma: On the design of a controlled experiment

To meet stakeholder non-technical background, requirements are often presented by analysts in terms of scenarios. While translating requirements into scenarios, details and over-specifications (called Ahab´s Legs) need to be added to make requirements concrete and understandable to stakeholders. Despite the expected benefits that they should convey, Ahab´s Legs could disturb the requirement validation session. They can, in fact, distract the attention of stakeholders. Valuable discussion time may be wasted when focusing on irrelevant details rather than on the actually relevant ones. In the present paper, we address the Ahab´s Leg dilemma and its potential impact on requirement validation sessions. We discuss how to measure the distraction due to Ahab´s Legs and what are the possible approaches an analyst can adopt to limit it. Moreover, we present the design of a controlled experiment devoted to measure the impact of Ahab´s Legs on requirement validation sessions. In particular, the experiment is meant to (1) estimate the magnitude of the distracting effect, and to (2) assess one of the most promising way to alleviate their negative effect, i.e. by making stakeholder aware of the Ahab´s Legs before the validation session.