Zooming In and Out in Requirements Engineering

In this paper we present some cognitive guidelines to move from higher degrees of abstraction to lower, more concrete degrees of abstraction, and reciprocally. For a time, in Requirements Engineering this approach was called the

top-down method

and it was intended to be used as a general method in the first steps of specifying a system: the whole application was decomposed using this method. In everyday analysis and design, it continues to be a fundamental way of separation of concerns, applying the motto of

divide and conquer

. In order to divide, we must visualize the whole system in terms of lower level components: processes, use cases or user stories. But the important question is that zooming in can not start –in Requirements Engineering– at every level but at a given level of abstraction, usually at the level where some event will trigger the execution of some processes: such is the case of user stories and use cases. Another important issue we want to stress is the essential role that stories play in our cognition: this is why user stories –as well as use cases– have been and continue to be intensively used in software development.